Conventional catalytic measurements typically combine the behavior of many particles, producing an average that can conceal substantial differences from one surface region to another. Local variations may hold important clues for materials design because a catalyst’s edges, side surfaces and broad faces can behave differently even when they share the same chemical composition. DELINE was developed to preserve this spatial information by recording where individual catalytic events occur while the catalyst is working, rather than reporting only an aggregate activity value. Assistant Professor Mao Xianwen, who led the research in the Department of Materials Science and Engineering at the NUS College of Design and Engineering, said the method can show which parts of a catalyst are active and how their behavior changes under different operating conditions.

The imaging approach links a catalytic reaction that does not itself emit light to a much faster follow-on reaction that produces fluorescence. A probe molecule reacts with a product of the original reaction, and the locations of the resulting fluorescent signals reveal the relative activity of different regions on the catalyst surface. This arrangement allows the researchers to sample individual events across a working material without requiring the reaction of interest to be fluorescent. Control experiments showed that the probe did not alter the catalytic activity of the gold, supporting the interpretation that the recorded signals reflected the underlying reaction rather than an effect introduced by the measurement system.

To demonstrate the method, the team used thin catalytic gold plates to examine water dissociation, a key step in producing hydrogen from water. During this process, water splits at the metal surface, leaving attached hydrogen that can subsequently form hydrogen gas. The reaction also generates hydroxide ions, described in the study as negatively charged groups containing oxygen and hydrogen. A probe molecule reacts with these hydroxide ions to create the fluorescent events detected by DELINE. The resulting reaction maps show not only whether a region is active but also how individual events are distributed across the material. By resolving individual reaction events, the method provides a way to examine catalytic heterogeneity while the electrocatalyst is under working conditions.

Across 39 gold plates, the researchers compared 195 surface regions. Edges and side surfaces were generally more active than the broad, flat faces of the plates, although activity also varied within the flatter areas. Such differences could disappear in conventional measurements that average the output of multiple particles. The observed variation prompted the team to vary the applied voltage and determine how strongly the water-dissociation reaction accelerated in each mapped region. They also estimated a baseline reaction rate at equilibrium, when forward and reverse reactions balance, to distinguish the underlying speed of a region from its response to electrical driving. The gold experiment was therefore designed to connect spatial maps of reaction activity with both equilibrium-rate estimates and voltage-dependent behavior.

The analysis exposed a trade-off: regions with a stronger response to voltage tended to have a lower baseline rate. These two effects can offset one another in a relationship known as kinetic compensation. The result means that a surface region that performs well under one set of electrical conditions may lose its advantage when those conditions change. For hydrogen production, this distinction matters because a catalyst with greater voltage sensitivity may require a smaller voltage increase to accelerate the reaction, making that sensitivity important alongside baseline activity. A design that emphasizes one property is therefore not necessarily the best option for every electrochemical device. This voltage-response and baseline-rate relationship was measured for water dissociation on gold; the copper tests demonstrated differences in which surface regions were active, rather than establishing the same trade-off there.

Computer simulations and additional surface imaging helped the researchers investigate the physical processes behind the gold trade-off. Sodium ions in the surrounding liquid accumulated unevenly near the gold surface, changing the environment around nearby water molecules and making their reaction more sensitive to voltage. The same ion accumulation could crowd the surface, slowing the movement and rearrangement of water and thereby reducing the baseline reaction rate. The experiments therefore connect a measurable pattern in catalyst activity with the local ionic environment and molecular behavior at the interface. The findings do not establish that the same mechanism applies equally to every catalyst, electrolyte or electrochemical reaction, and the authors presented DELINE as a method whose application to other systems would require further investigation.

The reaction maps were then used to calculate how hollow gold plates with different rim widths would perform. The calculations showed that widening the rim could either improve or reduce overall activity, depending on the applied voltage and the distribution of reactions across the surface. This result illustrates a practical way in which spatial imaging could guide material design: candidate geometries can be evaluated against the local reaction pattern of the material and the electrical conditions expected in a device. The study did not demonstrate a finished hydrogen-production device or establish a universally optimal shape. Instead, it showed how catalyst shapes could be selected with operating conditions and site-specific activity in mind, and how a feature that increases performance at one voltage can become less advantageous when conditions change.

Tests on copper showed that the most useful surface features can differ between materials and reactions. During water dissociation on copper plates, the broad, flat faces were more active than the edges, reversing the general pattern observed on gold. The researchers also applied DELINE to nitrate reduction, a process that converts nitrate into other nitrogen compounds. This reversal supports the need to identify active structures for each catalyst and reaction rather than assuming that edges, corners or flat surfaces will always be preferable. It also demonstrates that the imaging method is not restricted to the single reaction used for its initial gold demonstration. The experiments do not imply that flat surfaces are generally superior to edges: the observed ordering changed with the material, underscoring the need to characterize activity in the specific system under investigation.

DELINE can analyze approximately 100 particles within a single microscope field during a recording lasting about three minutes, allowing multiple particles to be compared under the same conditions. This throughput makes it possible to examine heterogeneous surfaces at a scale that would be difficult to resolve with an aggregate measurement alone. The team is now exploring new probe designs to extend the approach to additional electrically driven reactions, including nitrogen fixation, in which nitrogen gas is converted into chemically useful compounds. The researchers also aim to visualize catalytic processes inside operating batteries. Mao said the broader goal is to connect events on catalyst surfaces with practical choices about material design, while establishing which design principles transfer across systems and which must be tailored to a particular process. The study thus combines a single-event optical measurement advance with a design lesson: average catalyst activity alone may not identify the most useful surface structure for a specific operating environment.

Subject of Research: Single-turnover optical imaging of electrocatalytic water dissociation and kinetic compensation

Article Title: NUS CDE researchers map individual reactions to guide better catalyst design

Article References: NUS CDE researchers map individual reactions to guide better catalyst design. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: DELINE, electrocatalysis, water dissociation, kinetic compensation, gold catalyst, copper catalyst, single-turnover imaging, operando characterization, surface reactions, hydrogen production, researchers, individual

The stakes are high. Electrochemical CO2 reduction promises to convert captured carbon dioxide into valuable fuels and chemicals such as carbon monoxide, methane, ethylene and ethanol, offering a route to decarbonise chemical manufacturing and transport. Copper remains the most promising electrocatalyst for these products because its selectivity can be tuned, and specific facets and ensembles of copper atoms enable the carbon-carbon coupling steps that build multicarbon molecules. Yet decades of mechanistic studies have relied on idealised static surfaces and simplified adsorbate models, and the discrepancies between different in situ spectroscopy studies have persistently frustrated efforts to build a unified picture. Most past experiments were also performed at current densities far below those relevant to deployment, in cells whose stagnant electrolytes and non-uniform electric fields do not resemble a real electrolyser.

The Barcelona team tackled this problem on two fronts. First, they used a three-electrode open flow cell with 1 M potassium bicarbonate electrolyte, which supplies a continuous stream of CO2 and decouples thermodynamic driving forces from mass transport limits. Then they built a custom operando Raman spectroscopy platform integrated directly into a membrane electrode assembly, achieving optical access to the buried cathodic interface through the anion exchange membrane and the iridium oxide-coated titanium anode. This allowed them to record spectra during genuine continuous CO2 electrolysis across a broad range of current densities, all the way to one ampere per square centimetre, while product analysis proceeded in parallel through gas chromatography and high-performance liquid chromatography.

The key to their analysis lies in how water organises itself at an electrified interface. Liquid water is best viewed as a continuously evolving, disordered hydrogen-bond network, but individual molecules can be classified phenomenologically by how many hydrogen bonds they make: tetrahedral water with four hydrogen bonds, trihedral water with three, and isolated free water. These populations shift with potential, current density, surface coverage and local ionic environment, and they can be quantified from the hydrogen-oxygen stretching band of the Raman spectrum. The researchers deconvoluted the stretching envelope into Gaussian components centred near 3,200 and 3,400 reciprocal centimetres for the four- and three-hydrogen-bond waters respectively, and tracked how these populations evolved as current was applied.

What emerged was a strikingly non-monotonic story. At rest, interfacial water sat in a random orientation with a dominant four-hydrogen-bond character. As current density rose toward 0.1 A per square centimetre, the three-hydrogen-bond fraction climbed from about 45 percent to 84 percent, with molecules flipping into an H-down orientation that aligns their hydrogens toward the negatively charged surface. This population of three-hydrogen-bond water turned out to be the primary proton source for CO2 reduction, and its rise coincided with growing selectivity toward multicarbon products. The four-hydrogen-bond fraction fell correspondingly, dipping to a minimum of about 16 percent. Between 0.2 and 0.4 A per square centimetre the picture shifted again, and beyond 0.4 A per square centimetre both water types flipped to H-down configurations as the increasingly strong interfacial electric field took over.

To understand why, the team turned to ab initio molecular dynamics simulations run on copper surfaces with varying coverages of potassium cations and adsorbed species. The simulations revealed a division of labour: adsorbed potassium ions act as hydrogen-bond breakers, dismantling the interfacial water network, whereas adsorbed hydroxide, carbon monoxide and carbonate species act as hydrogen-bond makers, extending and stiffening the network. Increasing the number of potassium cations in the double layer dropped the four-hydrogen-bond water fraction from 0.70 to 0.45, while adding hydroxide at that same cation coverage restored it to 0.73. This explained the experimental oscillation: as the potential grows more negative, anion coverage falls and cation concentration rises, disrupting water order, until the accumulation of polar adsorbates such as hydroxide and carbonate reorders the network once more, making the interfacial layer increasingly ice-like and rigid.

The coupling between water structure and reaction intermediates was mapped with two-dimensional correlated Raman spectroscopy, a technique that compares intensity fluctuations across many spectra to reveal which vibrational modes change together and in what order. The analysis traced a sequential pathway: adsorbed carbon monoxide forms first, shifting from a low-frequency to a high-frequency band; adsorbed hydroxide then appears and stabilises the high-frequency carbon monoxide species; and that intermediate converts into a carbonaceous intermediate implicated in carbon-carbon coupling. A strong positive correlation between the three-hydrogen-bond water signal and the high-frequency carbon monoxide band confirmed that interfacial water physically rearranges to accommodate and stabilise the species needed for multicarbon products.

Then came the gating mechanism itself. Beyond roughly 0.2 A per square centimetre, hydroxide generation falls behind its removal through the anion exchange membrane, carbonate accumulates, and the four-hydrogen-bond water fraction rebounds. This denser, more ordered water layer restricts access of carbon dioxide and carbon species to the interface while providing abundant protons for the competing hydrogen evolution reaction. A control experiment feeding argon instead of CO2 produced nearly 90 percent faradaic efficiency for hydrogen with a similar four-hydrogen-bond water content, confirming that the ordered water layer gates access to the catalyst surface regardless of which reactants are present. Electrochemical performance tracked the spectroscopy closely: carbon dioxide selectivity peaked, multicarbon selectivity reached 45 percent and the hydrogen efficiency bottomed out at 0.2 A per square centimetre, precisely where hydroxide coverage and three-hydrogen-bond water were maximal and carbonate and four-hydrogen-bond water were minimal.

The practical implications are considerable. If the interfacial hydrogen-bond network is a design variable rather than background noise, it can be engineered. The authors suggest that surface functionalisation with hydroxyl, amine, imidazole or sulfonate groups, hydrophobic terminations that modulate water orientation, tailored electrolytes that control cation concentration, and selective water-exchange membranes could all be used to hold the interface in the productive regime. Carbon monoxide reduction studies, which eliminate the carbonate signals that complicate spectroscopy, could refine the picture further, since surface-bound hydrogen donors and intermediates could then be tracked cleanly.

What makes the work resonate beyond electrochemistry is the demonstration that at industrial current densities, the hardest problems may not be about the catalyst at all, but about water management at a scale of a few molecular layers. The same molecules that deliver protons for synthesis can also cement themselves into a barrier that chokes off the reaction. Seeing that gate open and close, molecule by molecule, while the electrolyser runs, gives catalyst and system designers for the first time a molecular target to aim for: not merely a better copper surface, but a better-ordered dance of water above it.

Subject of Research: Interfacial water structure and its role in gating CO2 electroreduction on copper catalysts at high current density

Article Title: Operando resolution of CO2 electrolysis interfaces at application-relevant current density reveals water gating

Article References: Guha, A., Seemakurthi, R. R., Polesso, B., Haldar, P., Ram, R., Pinilla-Sánchez, A., Mondal, I., Kernan, D., López, N., & García de Arquer, F. P. (2026). Operando resolution of CO2 electrolysis interfaces at application-relevant current density reveals water gating. Nature Catalysis. https://doi.org/10.1038/s41929-026-01620-w

Image Credits: AI Generated

DOI: 10.1038/s41929-026-01620-w

Keywords: CO2 reduction, electrocatalysis, copper catalyst, interfacial water, Raman spectroscopy, molecular dynamics, hydrogen evolution, membrane electrode assembly, hydrogen-bond network, multicarbon products, electrolyser, water gating

The study, led by Li Zhang and Siyuan Wang with Ying Zhang as corresponding author, focused on copper-based catalysts supported on two very different oxides: zinc oxide and silica. Rather than relying on the conventional routes of impregnation or coprecipitation that have dominated catalyst preparation for decades, the researchers turned to a formic acid reduction method, a synthesis strategy in which formic acid acts as the reducing agent that converts copper species into their active metallic or suboxide forms. The choice matters more than it might seem. How a catalyst is born often determines how it behaves, because the reduction step controls particle size, copper dispersion and the delicate balance between metallic copper and oxidized copper on the surface, all of which govern catalytic performance.

To understand why this balance is so critical, it helps to look at how copper catalyzes alcohol dehydrogenation in the first place. In the accepted picture, metallic copper sites activate the O-H and C-H bonds of the alcohol, while nearby cationic copper species can assist in stabilizing reaction intermediates. The ratio of Cu⁰ to the combined pool of Cu⁺ and Cu⁰ on the surface is therefore a key descriptor of activity. Too little metallic copper and the catalyst cannot efficiently abstract hydrogen; too much aggregation and the effective surface area collapses. The formic acid reduction method, the new study shows, threads this needle better than the classical alternatives, producing catalysts with finer copper dispersion and a favorable surface oxidation state.

The experimental campaign behind the paper was exhaustive. The team prepared Cu-ZnO and Cu-SiO2 catalysts via formic acid reduction and benchmarked them against counterparts made by impregnation and coprecipitation. They then interrogated the materials with a battery of characterization techniques: X-ray diffraction to probe crystalline phases, X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy to quantify surface copper oxidation states, scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy to visualize morphology and elemental distribution, Brunauer-Emmett-Teller analysis to measure surface area, temperature-programmed reduction to assess reducibility, and inductively coupled plasma optical emission spectrometry to confirm bulk composition. This multi-technique approach allowed the researchers to connect measurable structural features directly to catalytic behavior rather than relying on correlations alone.

The headline result is unambiguous: the Cu-ZnO catalyst made by formic acid reduction outperforms the versions prepared by impregnation and coprecipitation. But the more striking comparison emerged between supports. When both catalysts were prepared by the same formic acid route, Cu-SiO2 proved superior to Cu-ZnO across the board. The silica-supported material boasted a specific surface area of 101.59 square meters per gram, substantially larger than what the zinc oxide support could offer, and this translated into better copper dispersion, meaning more copper atoms were actually exposed at the surface where they could do chemical work rather than being buried inside large crystallites.

Surface analysis added a second layer of explanation. The Cu-SiO2 catalyst exhibited a Cu⁰/(Cu⁺+Cu⁰) ratio of 41.3 percent, a figure the authors identify as collectively accounting for the enhanced catalytic activity together with the dispersion and area advantages. In other words, the silica support not only spreads the copper more thinly and finely, it also leaves the surface in an oxidation state that favors the dehydrogenation chemistry. The team then tested copper loadings of 30, 35 and 40 percent, and at every loading level the Cu-SiO2 formulation consistently outperformed its Cu-ZnO counterpart, demonstrating that the support effect is robust rather than an artifact of one particular composition.

To move beyond empirical correlation and toward genuine mechanistic understanding, the researchers employed density functional theory calculations, the quantum mechanical workhorse of modern computational catalysis. The DFT models compared how sec-butanol adsorbs on simulated Cu-SiO2 and Cu-ZnO surfaces, and the results showed that the adsorption energy of sec-butanol on the Cu-SiO2 model is higher, in the favorable sense of stronger binding, than on Cu-ZnO. The hollow site of the copper surface, where a molecule sits above the center of a triangle of copper atoms, exhibited the most pronounced adsorption, with a calculated energy of -592,571.24 kilojoules per mole in the reported model. Stronger adsorption of the alcohol at these sites facilitates the dehydrogenation reaction by holding the substrate in an orientation conducive to hydrogen abstraction.

The calculations also addressed the products and co-products of the reaction. For the target ketone, MEK, and for atomic hydrogen, the relative adsorption energies on the Cu-ZnO model came out higher than on the Cu-SiO2 model, which has consequences for how the catalytic cycle closes. Hydrogen atoms stripped from the alcohol must recombine and leave the surface for the reaction to continue; the energetics of hydrogen handling on copper are therefore as important as the initial activation of the substrate. Synthesizing the experimental and computational evidence, the authors concluded that the active sites of the Cu-SiO2 catalyst are primarily located at hollow sites, whereas on the Cu-ZnO catalyst the reaction preferentially proceeds at top sites, the positions directly atop individual surface copper atoms, which offer lower relative adsorption energy.

What makes this work notable beyond the immediate numbers is its illustration of a broader principle in heterogeneous catalysis: synthesis route and support choice are not independent knobs but intertwined levers. The formic acid reduction method does not simply make the same catalyst faster or cheaper; it changes the microstructure, and the silica support amplifies those changes by providing a high-area canvas on which copper can disperse finely and maintain the right oxidation balance. For an industrial process like MEK production, where margins are tight and catalysts run for months in fixed-bed reactors, even modest gains in activity or selectivity per gram of copper can translate into meaningful economic and environmental savings, including lower reaction temperatures and reduced energy demand.

The study also situates itself within a growing body of literature on copper-catalyzed dehydrogenation of alcohols. Copper on silica has previously shown advantages in vapor-phase dehydrogenation of long-chain alcohols such as 1-decanol to aldehydes, and copper catalysts have been explored for converting ethanol to acetaldehyde and hydrogen, 2,3-butanediol to acetoin, and 1,4-butanediol to gamma-butyrolactone. The Shenyang group itself has prior work on fumed silica supported copper catalysts for sec-butanol dehydrogenation and on Cu-Ni/SiO2 formulations for the same reaction. The present contribution adds a synthesis-route dimension to this landscape, showing that formic acid reduction is a competitive and, in these tests, superior preparation strategy. Funded by the Liaoning Province Applied Basic Research Program, the Liaoning Provincial Department of Education, the Liaoning BaiQianWan Talents Program, the Shenyang Science and Technology Bureau and the National Natural Science Foundation of China, the research points toward a future in which green solvents like MEK are made with catalysts designed, atom by atom and site by site, from the very first step of their synthesis.

Subject of Research: Copper-based catalysts prepared by formic acid reduction for sec-butanol dehydrogenation to methyl ethyl ketone

Article Title: Application of Copper-Based Catalysts Prepared by the Formic Acid Reduction Method in the Dehydrogenation of Sec-butanol

Article References: Zhang, L., Wang, S., Zhao, Z., Chong, S., Zhou, H., & Zhang, Y. (2026). Application of Copper-Based Catalysts Prepared by the Formic Acid Reduction Method in the Dehydrogenation of Sec-butanol. Catalysis Letters, 156(11), Article 303. https://doi.org/10.1007/s10562-026-05514-1

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05514-1

Keywords: copper catalyst, formic acid reduction, sec-butanol, methyl ethyl ketone, dehydrogenation, SiO2 support, ZnO support, DFT calculations, heterogeneous catalysis, catalyst synthesis, copper dispersion, Catalysis Letters

The team, led by Ananth Govind Rajan, Associate Professor in the Department of Chemical Engineering at IISc, constructed a data-driven computational framework that maps nearly 10,000 elementary chemical reactions involved in converting CO2 into fuels and chemicals over a copper catalyst. The study, published in Nature Communications, demonstrates that a small, hand-picked reaction network can lead a model spectacularly astray, while a comprehensive, machine-learning-accelerated network brings predictions into line with laboratory reality. The work offers a template that could extend well beyond CO2 hydrogenation to other catalytic processes central to a sustainable energy economy.

The scale of the problem is easy to underestimate. In CO2 hydrogenation, CO2 reacts with hydrogen over a catalyst to yield products such as methanol and carbon monoxide, but each product emerges from a tangled web of intermediates adsorbed on the metal surface. Traditional mechanistic modelling relies on chemical intuition to select perhaps a few dozen likely reactions, because modeling even one reaction with methods such as density functional theory demands enormous computational resources. That intuition, the IISc researchers argued, carries a hidden risk: the network might quietly omit the one step that actually controls the outcome.

First author Anand Mohan Verma, who carried out the work as a CV Raman Postdoctoral Fellow at IISc and is currently an Assistant Professor at Motilal Nehru National Institute of Technology Allahabad, framed the central dilemma of the field. Mechanistic modellers can never be certain that a curated reaction network has not excluded the critical step, and that uncertainty undermines confidence in every downstream prediction. The new framework was designed specifically to eliminate that blind spot by replacing intuition with systematic enumeration.

The researchers began by generating a carefully curated database of 152 reactions using quantum-mechanical simulations, establishing a foundation of reliable energetics. They then trained machine learning models to rapidly predict activation energy barriers for additional reactions, borrowing the pattern-recognition strengths of modern artificial intelligence to sidestep the expense of calculating each barrier from first principles. In parallel, they deployed automated enumeration tools to identify every possible single-step reaction involving 105 distinct surface species. Combining these approaches expanded the original seed network to 9,389 elementary reactions, a catalog several orders of magnitude larger than anything a conventional modelling effort would attempt.

The payoff was immediate and dramatic. When the team modeled CO2 hydrogenation using only the initial 152 reactions, the network predicted that formic acid, not methanol, would emerge as the dominant product, and it badly underestimated how much CO2 would be converted overall. Only after expanding the network to include the thousands of previously overlooked reactions did the predictions align with experimental observations from the researchers’ own work and from published studies. Rajan emphasized that this discrepancy shows how small networks can produce qualitatively wrong answers while appearing perfectly rigorous on their own terms.

Plugged into a kinetic model, the expanded network predicted an approximately 40-fold increase in CO2 conversion compared with the sparse network, and it correctly identified methanol and carbon monoxide as the major products, matching what experiments actually deliver. Experimental validation was performed by collaborators G Valavarasu and Santhosh Kotni at Hindustan Petroleum Corporation Limited’s Green Research and Development Centre, and by Amol Amrute and colleagues at the Agency for Science, Technology, and Research in Singapore. The machine learning components drew on expertise from Ambedkar Dukkipati, Professor in the Department of Computer Science and Automation at IISc, underscoring the interdisciplinary character of the project.

The most conceptually striking result concerned hydrogen transfer. The enlarged network revealed that in several key steps, hydrogen can be delivered to reaction intermediates directly as intact molecular H2, rather than only through individual hydrogen atoms dissociated on the surface. Quantum-mechanical calculations performed explicitly on those steps confirmed that this molecular pathway can be particularly favourable for hydrogen transfer to oxygen-containing intermediates. This finding challenges a foundational assumption taught in catalysis courses, namely that H2 must first split into atoms before it can participate in surface chemistry, and it emerged purely because the network was large enough for the pathway to appear.

Shivam Chaturvedi, a PhD student in the Department of Chemical Engineering at IISc and co-author of the study, noted that the molecular hydrogen transfer pathway surfaced only because the reaction network was sufficiently expansive, and that the observation held up when the team returned to compute those specific steps with full quantum-mechanical rigor. The finding also carries practical implications for catalyst design. Catalysts that interact more strongly with H2 could potentially enhance the pathways leading to methanol, offering a concrete design principle for engineers seeking to improve the yield of this valuable fuel and chemical feedstock from CO2.

Beyond its immediate insights into copper-catalyzed CO2 hydrogenation, the framework represents a general strategy for exploring complex catalytic chemistry. By combining quantum-mechanical simulations for ground-truth energetics, machine learning for rapid interpolation across vast reaction spaces, automated enumeration for exhaustive coverage, and kinetic modelling for connection to observable outcomes, the approach can in principle be applied to other industrially important processes, including CO2 reduction on alternative catalysts, nitrogen reduction for ammonia synthesis, and water splitting for green hydrogen production. As decarbonization efforts intensify worldwide, tools that can map reaction landscapes comprehensively, rather than selectively, may prove decisive in turning atmospheric carbon into useful chemistry at scale.

Subject of Research: Data-driven computational mapping of catalytic CO2 hydrogenation reaction networks on copper

Article Title: Using machine learning and computation to unveil mechanisms for CO2-to-fuel conversion

Article References: Using machine learning and computation to unveil mechanisms for CO2-to-fuel conversion. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: CO2 hydrogenation, machine learning, copper catalyst, methanol synthesis, reaction networks, computational catalysis, density functional theory, kinetic modelling, catalyst design, hydrogen transfer, Nature Communications, carbon recycling

The challenge the team set out to solve is one of the deepest in catalysis. Ethane, the second-largest component of natural gas, is held together by carbon–hydrogen bonds that are among the least reactive in chemistry. Breaking one of these bonds selectively, and then persuading the resulting fragment to bond with a carbon monoxide molecule rather than simply burning to carbon dioxide or over-oxidizing into a soup of byproducts, has defeated generations of catalyst designers. Conventional approaches rely on high temperatures that push reactions toward complete combustion, destroying precisely the selectivity that makes a process commercially attractive.

The new work, led by Qi Lu of Tsinghua University together with Bingjun Xu of Peking University and Mu-jeng Cheng of National Cheng Kung University, sidesteps this problem by splitting the catalytic labor between two distinct chemical roles of the same metal. Adsorbed oxygen species on an oxidized copper surface are responsible for activating ethane, abstracting a hydrogen atom to create a surface ethyl species. Meanwhile, copper ions released from the surface oxide into the acidic solution form carbonyl species with dissolved carbon monoxide, and it is at the interface between these two worlds that the crucial carbon–carbon bond forms.

Carbon monoxide plays a double role in this scheme, and that dual function is central to the reaction’s unusual selectivity. It serves as the C1 building block that is inserted into the ethane-derived fragment, ultimately delivering the carboxylic acid functionality of propionic acid. But it also acts as a selectivity-directing agent, intercepting the reactive ethyl intermediates before they can drift into unproductive oxidation pathways. By capturing the C–H activation intermediate quickly, CO essentially funnels the chemistry toward a single desired product rather than the mixture of alcohols, aldehydes and acids that typically plagues partial oxidation of light alkanes.

The experimental evidence for this mechanism is unusually thorough. The team used isotopic labelling to confirm that both the two-carbon skeleton of the product derives from ethane and the single added carbon from carbon monoxide, ruling out alternative carbon sources. In situ surface-enhanced infrared and Raman spectroscopies, techniques the group has refined in earlier studies of carbon monoxide electroreduction on copper, allowed the researchers to watch copper carbonyl species and surface ethyl intermediates directly on the working catalyst. Density functional theory calculations performed by the Cheng group in Tainan provided the energetic underpinning, showing that interfacial coupling between the copper carbonyl and the ethyl species is feasible under the mild conditions of the experiment.

The performance numbers tell a story of deliberate trade-offs. At propionic acid formation rates of up to 120 micromoles per gram of copper per hour, the selectivity settles at around 50 percent. When the team tuned conditions to slow the rate, selectivity climbed to its optimum of 83 percent, indicating that the competing pathways can be suppressed at the cost of throughput. This rate–selectivity relationship is a familiar feature of partial oxidation chemistry, but the fact that both ends of the trade-off are respectable at ambient temperature is what distinguishes the result. The researchers suggest that the strategy establishes CO-mediated alkane carbonylation under mild conditions as a genuine synthetic platform for organic acid production.

The intellectual lineage of the work stretches back decades. Carbonylation, the insertion of carbon monoxide into metal–carbon bonds, is the backbone of some of the largest industrial processes on Earth, most famously the methanol-to-acetic acid route that feeds global demand for one of the most important commodity chemicals. Applying carbonylation to saturated hydrocarbons, however, has required either superacidic media, precious metal catalysts or harsh temperatures. Early hints came from work in the 1970s showing that copper(I) carbonyl cations could carbonylate saturated hydrocarbons in strong acids, and more recent studies have explored carbonylation of alkanes over zeolites and via photocatalytic hydrogen atom transfer. The new study brings these threads together in a heterogeneous, aqueous system that operates at room temperature.

Copper’s starring role is itself notable. The metal has enjoyed a renaissance in catalysis over the past decade, particularly in electrochemistry, where oxide-derived copper electrodes proved capable of converting carbon dioxide and carbon monoxide into multicarbon products such as ethanol and acetate. That literature established that copper carbonyl species on oxidized copper surfaces can engage in carbon–carbon bond formation, and the present work transplants that insight from electrochemistry into a purely chemical, oxygen-driven setting. The researchers’ earlier investigations into how carbon monoxide coverage governs coupling on copper surfaces clearly informed the design of the new reaction, illustrating how mechanistic understanding in one field can seed breakthroughs in another.

The sustainability implications are considerable. Ethane is abundant, cheap and often flared or simply burned as fuel in regions far from petrochemical infrastructure. Converting it directly into propionic acid, a preservative, feed additive and chemical intermediate currently produced largely through petrochemical routes, would add value to a stranded resource while avoiding the energy intensity of steam cracking or high-temperature oxidation. Running the reaction in dilute acid with molecular oxygen as the terminal oxidant, rather than stoichiometric oxidants or precious metals, keeps the reagent palette inexpensive and environmentally benign. The authors acknowledge that the current rates, while scientifically impressive, remain far from industrial scale, and that catalyst durability and reactor engineering will need attention before any commercial translation.

What makes the result resonate beyond its immediate application is the demonstration that the most inert bonds in organic chemistry can be tamed at ambient conditions when activation and functionalization are assigned to different, cooperating chemical environments on a single catalyst. The interfacial coupling concept, in which a surface-bound alkyl fragment meets a solution-phase carbonyl species precisely at the boundary between oxide and liquid, offers a design principle that could extend to methane, propane and other light alkanes. If the strategy generalizes, the humble copper surface, working quietly at room temperature, may become the stage on which natural gas is rewritten into the building blocks of the chemical industry.

Subject of Research: Room-temperature catalytic coupling of ethane and carbon monoxide to synthesize propionic acid over copper

Article Title: Propionic acid synthesis via room-temperature coupling of ethane and CO

Article References: Hou, J., Liu, W., Wang, K.-H., Li, M., Wen, S.-C., Cheng, M.-J., Xu, B., & Lu, Q. (2026). Propionic acid synthesis via room-temperature coupling of ethane and CO. Nature Synthesis. https://doi.org/10.1038/s44160-026-01168-4

Image Credits: AI Generated

DOI: 10.1038/s44160-026-01168-4

Keywords: catalysis, copper catalyst, ethane, carbon monoxide, propionic acid, carbonylation, C–H activation, selectivity, mild conditions, organic acids, sustainability, heterogeneous catalysis

The study, published in Catalysis Letters, addresses a problem that has plagued furfural hydrogenation for decades. When furfural meets a hydrogenation catalyst, it has two chemically distinct destinations. Hydrogen can add to the carbonyl group of the aldehyde, producing furfuryl alcohol, the desired product, or it can attack the furan ring itself, over-hydrogenating the molecule all the way to tetrahydrofurfuryl alcohol, which requires more hydrogen and more severe conditions. Side reactions such as acetalization with alcohol solvents, decarbonylation to furan, and condensation of furfuryl alcohol on acidic surfaces further erode the yield. The balance of these competing pathways is exquisitely sensitive to the chemistry of the catalyst surface, particularly the density and strength of acid sites on the support and the electronic and geometric state of the metal particles dispersed on it.

Copper has long been favored for this transformation because it preferentially hydrogenates the aldehyde function while leaving the aromatic furan ring untouched. But bare copper catalysts supported on acidic oxides suffer from two chronic weaknesses. First, strongly acidic support sites catalyze the resinification of furfural and furfuryl alcohol, converting valuable product into insoluble humins that poison the catalyst and lower selectivity. Second, copper particles sinter and oxidize under reaction conditions, progressively losing activity until the process must be shut down for regeneration. The Chinese team, comprising Qihang Ye, Zhaoping Zhong, Yuxuan Yang, Wei Wang, You Jia, Qi Xiong, Huanqi Chen, and Xiang Zheng, reasoned that a carbon layer introduced onto the catalyst support could simultaneously moderate the acid strength of the surface and shield the copper species from deactivation.

To test this hypothesis, the researchers prepared a family of carbon-modified, copper-loaded catalysts in which carbon-containing organic precursors were used to build a carbon encapsulation layer on the support before and during the dispersion of the copper active phase. The amount of carbon introduced became a tunable knob: too little carbon left the harsh acidity of the pristine support intact, while too much began to block pores and bury the very active sites the reaction depends on. Through systematic optimization of the carbon loading and of the reaction conditions, the team arrived at a configuration that delivered complete conversion of furfural with a furfuryl alcohol selectivity of 99.17 percent at a reaction temperature of just 160 degrees Celsius over four hours, using isopropanol as the solvent medium.

The mechanistic explanation for this exceptional performance emerges from a battery of characterization techniques the authors deployed, including X-ray diffraction, Brunauer–Emmett–Teller and Barrett–Joyner–Halenda porosimetry, scanning electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma analysis, hydrogen temperature-programmed reduction, Fourier-transform infrared spectroscopy, pyridine-adsorbed FTIR, and ammonia temperature-programmed desorption. Together, these measurements revealed that the carbon loading did something chemically subtle: it converted the strong acid sites on the support into medium-strong acid sites. That shift matters because strongly acidic sites promote the condensation and resinification side reactions that destroy furfuryl alcohol, whereas medium-strength sites can participate productively in adsorbing and activating furfural without triggering destructive chemistry.

Equally important was the second consequence of the carbon treatment: an increase in the ratio of Lewis to Brønsted acid sites on the catalyst surface. Lewis acid sites, which are coordinatively unsaturated metal or metal-oxygen centers, are known to coordinate the oxygen atom of the furfural carbonyl group, polarizing the carbon–oxygen double bond and making it more susceptible to hydrogen attack from adjacent copper sites. Brønsted sites, by contrast, donate protons and promote the oligomerization chemistry that generates the carbonaceous deposits known to clog and deactivate hydrogenation catalysts. By raising the Lewis-to-Brønsted ratio, the carbon layer effectively steered the surface population of acid sites toward the geometry that favors aldehyde activation and away from the one that accelerates deactivation. The well-dispersed copper species identified on the carbon-modified surface then supply the hydrogenation function, working in concert with the re-engineered acid sites in a bifunctional arrangement that has become the design paradigm for modern furfural conversion catalysts.

Durability, the quality that separates laboratory curiosities from industrial candidates, was demonstrated through five consecutive catalytic cycles, in which the carbon-encapsulated catalyst maintained its high furfuryl alcohol selectivity with only minor losses in performance. The authors attribute this stability to two reinforcing features: the protective carbon layer, which physically and chemically shields the underlying support from direct contact with reactive intermediates and slows the migration and sintering of copper, and the consistently well-dispersed state of the copper species on the catalyst surface, which preserves the high density of accessible active sites cycle after cycle. Thermogravimetric analysis supported the picture of a catalyst resistant to the carbon deposition that degrades unmodified analogues, a conclusion with direct implications for the economics of continuous biomass upgrading operations where catalyst replacement and regeneration costs dominate operating budgets.

To probe the chemistry at the molecular level, the team turned to density functional theory calculations using the Vienna Ab initio Simulation Package, employing the Perdew–Burke–Ernzerhof generalized gradient approximation with projector augmented-wave potentials and analyzing the density of states and projected density of states of the adsorption configurations. The computations showed that furfural preferentially adsorbs on the catalyst surface through the η¹(O)-aldehyde configuration, meaning the molecule anchors through a single oxygen atom of the carbonyl group rather than lying flat through the furan ring. This adsorption geometry is precisely the one that exposes the carbonyl carbon to hydrogenation while protecting the ring from over-reduction, and its energetic preference on the carbon-modified surface provides a quantum-mechanical explanation for both the selectivity and the promotional role of the carbon layer observed experimentally. In effect, the surface chemistry funnels furfural down the furfuryl alcohol pathway by making the correct orientation of the adsorbed molecule the most stable one.

The broader significance of the work lies in how it reframes catalyst design for biomass valorization. Rather than treating carbon in a catalyst purely as a mechanical coating or an inert dopant, the study demonstrates that carbon loading functions as an electronic and acidic regulator, one that can be introduced with inexpensive organic precursors and tuned to shift the surface acidity, the Lewis-to-Brønsted balance, and the microenvironment of the metal phase all at once. Because furfural is produced at the scale of hundreds of thousands of tons per year and furfuryl alcohol commands a substantial premium over its parent aldehyde, even incremental gains in selectivity translate into meaningful economic and environmental returns, reducing hydrogen consumption, solvent losses, and waste generation. The results also dovetail with a growing body of literature on carbon-encapsulated and carbon-coated metal catalysts for furfural and cinnamaldehyde transformations, suggesting that the carbon-layer strategy discovered here may generalize to other oxygenate upgrading reactions across the platform-chemical landscape.

The research was supported by the National Key Research and Development Program of China, the China Postdoctoral Science Foundation, and the Taizhou Key Science and Technology Programme Projects. Corresponding author Zhaoping Zhong and his colleagues emphasize that data will be made available on request, and the team reports no competing interests. With a near-perfect selectivity achieved at moderate temperature, a catalyst that survives five reaction cycles intact, and a mechanistic narrative that connects carbon engineering to acid-site chemistry and first-principles adsorption energetics, the study offers the furfural industry a concrete blueprint for next-generation hydrogenation catalysts built from abundant copper and a whisper of carbon. As biomass-derived molecules continue their march into the fuel and chemical sectors, the ability to sculpt a catalyst surface with something as humble as a carbon layer may prove to be one of the quiet breakthroughs on which the bioeconomy’s chemical foundations are rebuilt.

Subject of Research: Carbon-layer-modified copper catalysts for the selective hydrogenation of biomass-derived furfural to furfuryl alcohol.

Article Title: Cu-Loaded Catalysts for Efficient Hydrogenation of Furfural to Furfuryl Alcohol: Modulation of Hydrogenation Performance by Introducing Carbon Layer

Article References: Ye, Q., Zhong, Z., Yang, Y., Wang, W., Jia, Y., Xiong, Q., Chen, H., & Zheng, X. (2026). Cu-Loaded Catalysts for Efficient Hydrogenation of Furfural to Furfuryl Alcohol: Modulation of Hydrogenation Performance by Introducing Carbon Layer. Catalysis Letters, 156(10), Article 282. https://doi.org/10.1007/s10562-026-05493-3

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05493-3

Keywords: Furfural, Hydrogenation, Furfuryl alcohol, Copper catalyst, Carbon-encapsulated catalyst, Lewis acid sites, Brønsted acid sites, Biomass valorization, Catalytic stability, DFT calculations, Selective hydrogenation, Platform chemicals

The core problem the researchers set out to solve is well known in the electrochemistry community. Copper remains the only metal catalyst that can convert CO2 into multi-carbon products at appreciable rates, because its binding energies sit in a narrow window that permits carbon–carbon coupling. Yet even the best copper-based systems overwhelmingly favor two-carbon products such as ethylene and ethanol, while the formation of C3+ hydrocarbons and oxygenates—propane, butane, propanol, butanol and other chemicals that command higher market value—remains stubbornly inefficient. Decades of catalyst design, from oxide-derived copper to facet-engineered films and tandem catalytic cascades, have delivered incremental gains, but the underlying reaction network on copper constrains which intermediates can form and, ultimately, which products can emerge.

The Yale–Antwerp team took a different approach: instead of redesigning the catalyst, they redesigned the feedstock. In their platform, CO2 or CO gas first passes through a non-thermal plasma, where energetic electrons collide with gas molecules and generate a rich cocktail of vibrationally excited molecules, radicals, dissociation fragments and unusual species such as carbon suboxide, C3O2. This activated gas stream is then delivered directly to a copper gas diffusion electrode, where the electrocatalytic reduction takes place. Crucially, by coupling the plasma to a gas-phase electrode rather than bubbling plasma products through an electrolyte, the design ensures that short-lived, highly reactive species survive long enough to reach the catalyst surface, where their stored chemical energy can be harvested electrochemically.

The results are striking. When CO2 and CO were co-fed through the plasma into the electrochemical cell, productivity of C3+ products increased by a factor of 3.3 and alcohol productivity by 1.5 times relative to electrocatalysis alone. Even more remarkable is the selectivity expansion: plasma activation unlocked the formation of chemicals that are essentially absent from purely electrocatalytic product distributions, including methanol, acetylene, ethane, propane, butane and butanol. In other words, the plasma does not simply accelerate the standard copper chemistry—it opens entirely new reaction channels on the same metal surface.

To understand why, the researchers combined plasma simulations, kinetic modeling and in situ spectroscopy. Plasma simulations of the discharge revealed that a significant fraction of CO2 molecules leaves the plasma vibrationally excited rather than fully dissociated. Vibrational excitation is a form of chemical currency: a vibrationally hot CO2 molecule effectively carries part of the activation energy needed for its own reduction, lowering the energetic barrier for subsequent steps at the electrode. Kinetic simulations comparing plasma-excited and ground-state species showed that these excited molecules, once adsorbed on copper, can follow different reaction trajectories than their thermal counterparts, enriching the population of key surface intermediates that feed C–C coupling and oxygenate formation.

Carbon suboxide emerged as another central player. This unusual C3O2 species, long studied in combustion and plasma physics, is generated in the plasma through reactions of CO with excited CO2. The team’s kinetic simulations and in situ analysis suggest that carbon suboxide arriving at the copper surface can be reduced and hydrogenated along pathways that bypass the conventional CO dimerization route, providing a direct entry point into three-carbon products. The in situ Raman spectroscopy experiments, performed by the Yale group on operating copper electrodes, tracked changes in surface adsorbates when plasma-activated gas was introduced, providing experimental evidence that the plasma species reshuffle the intermediate landscape on the catalyst rather than merely increasing local reactant concentration.

The gas diffusion electrode architecture deserves particular attention. Gas diffusion electrodes have become the workhorse of modern CO2 electrolysis because they bring the gaseous reactant into intimate contact with the catalyst at a three-phase boundary, enabling current densities that far exceed what submerged electrodes can achieve. The researchers deliberately designed the plasma outlet to feed the activated gas stream directly into the gas diffusion layer of the copper electrode, minimizing the residence time between plasma and catalyst. This tight coupling prevents the reactive plasma species from being consumed by recombination reactions or neutralized in the liquid electrolyte—a failure mode that has plagued earlier attempts to combine plasma with electrochemistry in solution-phase cells.

The team systematically varied the operating conditions to disentangle the contributions of different plasma species. Comparing pure CO2 feeds, pure CO feeds and mixed CO2–CO feeds through the plasma showed that the presence of both gases in the discharge enhanced C3+ and alcohol formation beyond what either gas alone could achieve, consistent with the formation of carbon suboxide requiring both CO2 and CO in the plasma zone. Varying the applied electrode potential mapped out how the electrochemical driving force interacts with the chemically activated feed, showing that the plasma effect persists across the potential window relevant to multi-carbon production. Plasma diagnostic experiments on the discharge itself complemented the modeling, anchoring the simulated species distributions in measured reality.

Beyond the mechanistic insights, the work carries significant implications for how renewable electricity might be converted into storable fuels and industrial feedstocks. Electrosynthesis of chemicals from CO2 promises a route to close the carbon cycle using intermittent solar and wind power, but the technology’s economic viability hinges on achieving high rates, high selectivity and high value products simultaneously. By demonstrating that plasma activation can raise production rates of the most valuable C3+ products by more than threefold while adding entirely new product classes, the platform addresses the selectivity bottleneck in a fundamentally new way—as a feedstock activation problem rather than a catalyst design problem. The two technologies are complementary by nature: plasma excitation is fast, catalyst-agnostic and tolerant of dilute feeds, while electrocatalysis offers precise control over electron transfer and product distribution at ambient temperature and pressure.

The researchers are candid that scaling the concept will require attention to energy efficiency, since both plasma generation and electrochemical reduction consume electricity, and the overall energy conversion chain must compete with incumbent fossil-based processes. Stability of the coupled reactor over extended operation, integration of the plasma unit with industrial gas handling, and optimization of discharge type and power coupling all represent engineering challenges ahead. A patent application covering the plasma–electrocatalysis flow cell has been filed by Yale, signaling the team’s intent to translate the concept. Still, the demonstration that vibrationally excited molecules and carbon suboxide can rewrite the reaction network on copper offers the field a genuinely new lever. If the synergy between plasma chemistry and electrocatalysis can be pushed further—through tailored discharge conditions, optimized gas residence times and catalyst surfaces designed to accept plasma species—the electrosynthesis of high-value chemicals and fuels from CO2 could move meaningfully closer to practical reality.

Subject of Research: Plasma-activated electrocatalytic conversion of CO2 and CO to C3+ hydrocarbons and oxygenates on copper

Article Title: Unlocking reaction pathways for CO2 and CO electrocatalytic reduction to C3+ hydrocarbons and oxygenates using plasma activation

Article References: Kim, J.-Y., Biondo, O., Gao, Y., Anderson, K., Simon, J., Fan, Y., Wang, H., Bogaerts, A., & Winter, L. R. (2026). Unlocking reaction pathways for CO2 and CO electrocatalytic reduction to C3+ hydrocarbons and oxygenates using plasma activation. Nature Catalysis. https://doi.org/10.1038/s41929-026-01609-5

Image Credits: AI Generated

DOI: 10.1038/s41929-026-01609-5

Keywords: CO2 reduction, electrocatalysis, non-thermal plasma, copper catalyst, C3+ products, oxygenates, carbon suboxide, vibrational excitation, gas diffusion electrode, plasma-electrocatalysis, renewable fuels, Nature Catalysis

The new work arrives at a moment when CO2 electroreduction stands at a crossroads. Laboratory demonstrations of copper-based catalysts converting carbon dioxide into ethylene, ethanol and other multicarbon products have multiplied rapidly over the past decade, but translating those results into industrial electrolyzers capable of gigatonne-scale operation demands catalysts that remain active, selective and stable for thousands of hours. Catalyst reconstruction sits at the heart of that challenge. When a copper catalyst reorganizes itself under operating conditions, its activity can rise or fall, its product selectivity can drift toward desired chemicals or toward wasteful hydrogen evolution, and its lifetime can be cut dramatically short. Until now, the field has lacked a standardized, reproducible methodology for investigating these transformations—leaving individual laboratories to improvise their own approaches, with results that are often difficult to compare or reproduce.

The protocol is organized around what the authors call a ‘reconstruction–understanding–intervention’ workflow, a modular pipeline that guides researchers from the first observation of structural change all the way to deliberate control of the catalyst’s final state. The first stage involves the identification and taxonomy of reconstruction phenomena, classifying the many ways a copper surface can transform: morphological reshaping, chemical state changes such as the reduction of copper oxides to metallic copper or the persistence of transient copper(I) species, and compositional evolution in alloyed or bimetallic systems. By establishing a common vocabulary and systematic identification procedures, the protocol addresses one of the field’s most persistent problems—different groups describing fundamentally different phenomena under the same broad label of ‘reconstruction’.

The second stage tackles the question of what drives these transformations in the first place. Reconstruction is governed by an interplay of electrochemical and environmental factors: applied potential, local pH, the identity and concentration of electrolyte cations and anions, mass transport of CO2 to the surface, and the adsorption of reaction intermediates such as carbon monoxide. The protocol lays out quantitative methods for disentangling these variables, allowing researchers to determine whether a particular restructuring event is triggered by potential cycling, by the accumulation of hydroxyl species, by the migration of alkali metal cations into the interfacial layer, or by some combination of influences. This quantitative grounding is essential, because interventions can only be rationally designed once the governing factors are known.

At the technical core of the protocol lies a battery of complementary in situ and operando characterization techniques, each chosen to illuminate a different aspect of the catalyst’s evolving structure. Operando Raman spectroscopy tracks surface oxides, adsorbed intermediates and the formation of species such as copper carbonyl in real time under working conditions. Infrared spectroscopy, including surface-enhanced variants based on attenuated total reflection, probes the vibrational fingerprints of adsorbed molecules and interfacial water networks. X-ray absorption spectroscopy, typically performed at synchrotron facilities, reveals changes in the oxidation state and local coordination environment of copper atoms deep within the working electrode. Quasi-in situ X-ray photoelectron spectroscopy bridges the gap between fully operando measurements and conventional ex situ analysis: the protocol describes a compact titanium-alloy transfer cell, sized to pass through a glovebox antechamber, that allows electrodes to be interrogated at defined electrochemical states without exposure to air, preserving chemical information that would otherwise be lost.

The methodological rigor extends to the hardware itself. The protocol provides detailed descriptions of electrochemical cell configurations—flow cells, gas diffusion electrode assemblies and spectroscopy-compatible electrolytic cells—because the authors emphasize that the very design of the cell influences how catalysts reconstruct. Extended data accompanying the article specify, for example, the geometry of an operando Raman flow cell built from polyetheretherketone with a titanium flow field and quartz optical window, and the configuration of an operando XAS cell sealed with Kapton film and oriented at 45 degrees to the incident X-ray beam. Standardizing these details means that structural dynamics observed in one laboratory can be meaningfully compared with results from another, a prerequisite for building a reliable, field-wide picture of copper’s behavior under reaction conditions.

With identification and diagnosis in hand, the protocol’s third pillar moves into territory that sets it apart: active intervention. Rather than treating reconstruction as an inevitable degradation process to be tolerated, the authors present three primary strategies for steering it toward desired active states. The first is catalyst structure modulation, in which the starting material—its composition, oxide content, strain and dopant profile—is engineered so that the reconstruction pathway terminates at a favorable configuration. The second is electrochemical operation regulation, including pulsed or intermittent electrolysis protocols that periodically reset or regenerate the catalyst surface. The third is reaction microenvironment management, in which the electrolyte composition, local hydrophobicity, cation distribution and interfacial water structure are tuned to stabilize particular surface states and suppress destructive pathways.

The methodology was validated across representative classes of copper catalysts, demonstrating its breadth. Commercial metallic copper foil, oxide-derived copper—the family of catalysts in which pre-formed oxides reorganize during reaction to create highly active surfaces—and bimetallic copper-based systems denoted Cu–X, where a second metal tunes copper’s electronic structure, all serve as test cases. In each case, the workflow linked specific reconstruction dynamics to catalytic behavior and showed that deliberate control strategies enhanced both performance and stability of CO2 reduction. The validation examples map onto the team’s own published record, including work on oxophilicity-controlled multicarbon alcohol production over Lewis-acid-doped copper, lanthanide-induced tensile-strained copper oxide catalysts, acid-fed lanthanum–copper spheres operating at ampere-level currents, in situ periodic regeneration of catalysts, and self-adaptive catalysts for CO2 electroreduction.

The broader significance of the protocol extends well beyond copper. The authors explicitly frame the workflow as an adaptable framework for investigating dynamic surface evolution in other electrocatalytic reactions, from nitrate reduction to ammonia—where correlated operando microscopy and spectroscopy have similarly revealed restructuring—to carbon monoxide reduction and beyond. As the global push toward carbon neutrality intensifies, the ability to design ‘self-adaptive’ electrocatalysts that respond constructively to their operating environment, rather than degrading under it, is emerging as a defining goal of the field. By providing a reproducible, modular and quantitative path from observation to mechanistic insight to rational control, this protocol gives the community a shared toolkit for reaching that goal. In effect, it transforms one of electrocatalysis’s most stubborn complications into an engineering variable—one that can be measured, modeled and ultimately mastered in the service of converting waste carbon dioxide into the fuels and chemicals of a sustainable economy.

The scientific backdrop to this protocol is a decade of discoveries that progressively dismantled the assumption of a static copper surface. Operando studies have shown that metallic copper can fragment into active nanograins under reaction conditions, while solution-based transient copper(I) species have been identified as mediators of surface reconstruction. Other work has revealed that oxygen trapped within oxide-derived copper can diffuse and persist during catalysis, and that hydroxyl radicals play a decisive role in reoxidizing reduced copper surfaces. Adsorbed hydroxide itself has been described as a double-edged sword, simultaneously promoting carbon–carbon coupling and destabilizing the catalyst. Each of these findings underscores why a single snapshot of a catalyst before or after electrolysis is insufficient: the active state may exist only transiently, sandwiched between structural configurations that are themselves catalytically inert.

The protocol also responds to a subtler problem: the observation itself can depend on how it is made. Recent comparative studies have demonstrated that cell configuration measurably alters how copper reconstructs, since flow geometry, electrolyte layer thickness and local mass transfer shape the interfacial chemical environment. Operando X-ray absorption work has quantified these mass-transfer effects directly, showing that concentration gradients near the electrode influence both the reaction pathway and the structural evolution of the catalyst. By specifying standardized cell geometries and measurement procedures, the protocol helps ensure that apparent differences between catalysts reflect genuine materials behavior rather than apparatus artifacts.

Another theme the protocol consolidates is the mechanistic link between reconstruction and selectivity. Spectroscopic observations of carbon monoxide bridge species forming on dynamically restructured copper, together with reconstruction-dependent coordination descriptors, suggest that the evolving surface geometry directly tunes how intermediates bind and couple. This reframes selectivity in CO2 electrolysis as a property of a moving target. The practical consequence is that stability and performance can no longer be optimized independently; a protocol that treats the catalyst’s trajectory through time as the design object, rather than its initial composition, aligns catalyst development with how these materials actually behave in operating electrolyzers.

Subject of Research: Dynamic reconstruction of copper-based catalysts during electrochemical CO2 reduction and methods for probing and controlling it

Article Title: Probing and controlling Cu catalyst reconstruction during CO2 electroreduction

Article References: Zhang, L., Zheng, C., Xu, L., Feng, J., Jia, S., Wu, L., Song, X., Zhang, M.-D., Wang, R., Zhang, X., Zhao, Z., Sun, X., & Han, B. (2026). Probing and controlling Cu catalyst reconstruction during CO2 electroreduction. Nature Protocols. https://doi.org/10.1038/s41596-026-01430-1

Image Credits: AI Generated

DOI: 10.1038/s41596-026-01430-1

Keywords: CO2 electroreduction, copper catalyst, catalyst reconstruction, electrocatalysis, operando spectroscopy, Raman spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, multicarbon products, catalyst stability, oxide-derived copper, carbon neutrality

Click chemistry has been a cornerstone of modern bioconjugation since the early 2000s, prized for reactions that run cleanly, at high yield, and with minimal side products under mild aqueous conditions. The workhorse of the family is the copper(I)-catalyzed azide-alkyne cycloaddition, or CuAAC, in which an azide group and a terminal alkyne snap together into a stable triazole ring. For biosensor makers, this offers a gentle way to tether receptors, fluorophores, or nanomaterials to a surface without damaging delicate biological molecules. The catch has always been the catalyst: copper(I) is unstable in oxygenated water, so traditional protocols add chemical reducing agents such as ascorbate to generate it in bulk, which gives little control over where or when the reaction happens.

The E-click approach solves that problem elegantly. Instead of dosing the solution with a reductant, the researchers used the electrode itself to electrochemically convert copper(II) into copper(I) right at the surface, on demand. Because the catalytic species is born only where the electrode is switched on, functionalization can be turned on and off with a potentiostat, confined to selected electrodes in an array, and tuned by adjusting the applied potential. This stands in contrast to conventional modification techniques such as physisorption, entrapment, molecular imprinting, or self-assembled monolayers, which can suffer from variable reaction efficiencies, limited site control, and sensitivity to pH, ionic strength, and temperature. It also offers an alternative to other electrochemical patterning tools such as light-activated electrochemistry and scanning electrochemical microscopy.

To test the concept, the team built a model biosensor surface step by step on gold substrates. First, they cleaned the gold electrochemically in sulfuric acid and immersed it in 11-mercaptoundecanoic acid, or MUA, which self-assembles into an ordered monolayer tipped with carboxylic acid groups. Next, standard EDC/NHS coupling chemistry was used to attach propargyl-PEG2-amine, presenting terminal alkyne groups at the surface. Finally, the stage was set for the click reaction: a fluorescent azide-tagged dye, FAM azide 6-isomer, served as a stand-in for a biological receptor, so that successful coupling could be read out directly from the surface’s emission spectrum. The copper(I) catalyst was generated in situ by applying a negative potential to the gold electrode in a solution of copper sulfate and sodium chloride.

Verifying that every step had worked required a battery of complementary techniques. X-ray photoelectron spectroscopy traced the chemical evolution of the surface, revealing carbon, nitrogen, and oxygen peaks consistent with the MUA monolayer, the EDC/NHS-coupled propargyl layer, and the final FAM attachment, along with copper oxide residues from the catalytic step. Crucially, sulfur 2p signals remained intact after the full procedure, showing that the underlying self-assembled monolayer had survived the electrochemical treatment without desorbing. Cyclic voltammetry in a ferrocyanide solution tracked the blocking of electron transfer as the monolayer formed, while electrochemical impedance spectroscopy, fitted to a Randles circuit, quantified the changing charge-transfer resistance at each step. Contact angle measurements rounded out the picture, shifting with the growing polarity and then hydrophobicity of the modified surface.

With the chemistry validated, the researchers turned to optimization, and the results carry practical lessons for anyone building sensors this way. Varying the reaction duration at a fixed potential of minus 0.35 volts showed that fluorescence, and therefore the amount of bound dye, rose linearly for the first ten minutes before saturating, indicating a rapid reaction and a surface approaching full coverage by roughly thirty minutes. The team settled on ten minutes as the sweet spot balancing signal, reproducibility, and handling time. Controls incubated without any applied potential showed only weak nonspecific adsorption, confirming that the coupling truly depends on electrochemically generated catalyst.

The applied potential proved to be the trickiest variable. Cyclic voltammetry of the copper electrolyte on the modified surface showed that the organic layers slow electron transfer, pushing the copper(II) to copper(I) reduction to more negative potentials and obscuring the peaks that would normally signal a viable condition. Potentials milder than about minus 0.25 volts failed to generate enough catalyst, while pushing beyond roughly minus 0.325 volts triggered unwanted copper deposition onto the surface, visible as nucleation loops and stripping peaks in the voltammograms. The usable window is narrow, and the authors identify minus 0.35 volts as a practical compromise that generates catalyst efficiently while minimizing surface damage. The fluorescence data confirmed that even potentials showing no obvious voltammetric signature could still drive the reaction, underscoring how subtle the choice of operating conditions can be on complex functionalized surfaces.

The most eye-catching demonstration, however, moves the catalyst off the sample altogether. In a proof of concept, the researchers used a conductive atomic force microscopy cantilever as the working electrode, scanning it over a propargyl-functionalized gold surface while holding it at minus 0.35 volts relative to the substrate. The copper(I) generated near the cantilever catalyzed click reactions along the scanned region, and subsequent fluorescence spectroscopy confirmed the characteristic FAM emission on the surface. In the current setup, functionalization was not confined to the scanned area alone, because the platinum-iridium coating covers the entire front face of the cantilever and generates catalyst over a broad zone. The authors note that cantilevers insulated everywhere except at the very tip could shrink the reaction zone to the nanoscale, enabling direct-write patterning of recognition molecules.

The implications reach well beyond a fluorescent demo. Electrode arrays for multiplexed diagnostics could have each electrode functionalized with a different receptor simply by addressing them individually, leaving neighbors untouched, a capability previously shown for microelectrodes but now extended to a scanning-probe geometry. Nanoarrays, multi-analyte sensors, and nanoengineered surfaces for fundamental studies of biomolecular recognition all come within reach if the tip-localized version matures. At the same time, the study is candid about its challenges: the narrow potential window for catalyst generation on modified surfaces, the risk of copper deposition at excessive overpotentials, and the difficulty of reading the copper reduction peak through an insulating organic layer. Solving these will matter for translating E-click from the bench to robust device fabrication.

What the Aalborg and Newcastle team has delivered is a careful, quantitative map of how an electrically triggered click reaction behaves on a realistic biosensor surface, complete with the spectroscopic fingerprints, electrochemical signatures, and wetting behavior that document every step. By showing that the same chemistry works whether the catalyst is born at the flat electrode or at the tip of an AFM cantilever, they have sketched a versatile platform for surface engineering in which a potentiostat, rather than a photomask or a chemical bath, dictates exactly where molecules attach. As biosensors push toward denser arrays, smaller samples, and higher sensitivity, the ability to write functional chemistry with spatial and temporal precision, using nothing more than a carefully chosen voltage applied for ten minutes, may prove to be one of those quiet enabling technologies that reshapes how sensing devices are made.

Subject of Research: Electrochemically driven click chemistry for controlled and localized biosensor electrode surface functionalization

Article Title: Electrochemical click chemistry for controlled and localized biosensor surface functionalization

Article References: Pedersen, T., Pike, A., Cucinotta, F., Horrocks, B. R., & Gurevich, L. (2026). Electrochemical click chemistry for controlled and localized biosensor surface functionalization. Discover Electrochemistry, 3(1), Article 74. https://doi.org/10.1007/s44373-026-00160-z

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00160-z

Keywords: electrochemical click chemistry, CuAAC, biosensor functionalization, self-assembled monolayer, copper catalyst, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, AFM cantilever, surface patterning, multiplexed biosensors, gold electrodes