The core of the problem is chloride. Seawater carries a high concentration of chloride ions, and at the cathode of a seawater air battery these ions behave as aggressive interlopers. They adsorb onto the very metal centers that are supposed to bind oxygen intermediates, blocking active sites, degrading catalytic performance and accelerating the corrosion of the catalyst layer itself. Iron-based single-atom catalysts, prized for their high intrinsic oxygen reduction activity in alkaline conditions, are particularly vulnerable. The result is a painful trade-off: catalysts that are highly active on the bench tend to lose their edge quickly in real seawater, while corrosion-resistant materials are often too sluggish to deliver competitive power.

The Hainan University group, led by corresponding author Peng Rao, approached this dilemma with a concept they describe as p-d orbital hybridization. Instead of leaving iron atoms to fend for themselves on a carbon support, the researchers paired each iron active site with an adjacent tin atom, creating what is known as a dual single-atom catalyst. Tin, a p-block element with its own distinct orbital character, does not simply sit nearby as a passive neighbor. Through overlap between its p orbitals and the d orbitals of iron, it reshapes the local electronic structure of the iron center, tuning how strongly the site binds oxygen-containing intermediates and how hospitably it treats chloride ions in the surrounding electrolyte.

This electronic engineering addresses a well-known limitation of conventional iron sites. In many iron-nitrogen-carbon catalysts, the binding of oxygen reduction intermediates is too strong, meaning that reaction intermediates such as hydroperoxyl species linger on the surface longer than they should and slow the overall turnover of the catalyst. The Fe-Sn interaction weakens this overly strong adsorption into a more favorable intermediate regime, while simultaneously creating a locally negatively charged interface around the iron site. Because chloride ions are negatively charged, that charged microenvironment electrostatically discourages them from approaching and poisoning the active center. In effect, the catalyst builds a nanoscale fence around its most valuable atom.

The design did not emerge by guesswork. The team first carried out density functional theory calculations, comparing several candidate pairings of iron with different p-block metals in dual-site configurations. Among the candidates, the iron-tin combination stood out with the best balance between oxygen reduction activity and chloride resistance, providing the theoretical justification for an ambitious synthesis. The researchers then produced the material using what they call a movable-type printing strategy, a modular approach that positions the two metal precursors with atomic precision on a nitrogen-doped carbon support before activation locks them into place.

Advanced characterization confirmed that the synthesis had achieved its goal. Microscopy and X-ray spectroscopy showed that both iron and tin were atomically dispersed across the carbon framework, stabilized as adjacent dual single-atom sites rather than clustering into nanoparticles. That atomic dispersion matters enormously. It maximizes the density of accessible active sites, ensures that every iron atom benefits from a tin neighbor, and prevents the formation of larger metal particles that could serve as initiation points for corrosion in the harsh chloride-rich environment.

Electrochemical testing in alkaline seawater electrolyte delivered striking results. The FeSn dual single-atom catalyst achieved a half-wave potential of 0.900 volts versus the reversible hydrogen electrode, outperforming both single-metal iron and tin catalysts prepared in the same way and beating commercial platinum-on-carbon, the traditional benchmark for oxygen reduction. The catalyst followed a near four-electron oxygen reduction pathway, the most efficient route that converts oxygen directly to hydroxide and delivers the maximum possible cell voltage. Equally important for real deployment, the material showed negligible activity decay after 30,000 accelerated durability test cycles, a punishing stress test that simulates years of charge-discharge operation.

Perhaps the most convincing evidence came from post-mortem analysis. After extended testing in the chloride-laden electrolyte, X-ray photoelectron spectroscopy revealed no observable iron-chloride signal on the catalyst surface, indicating that chloride adsorption on the iron active sites had been effectively suppressed throughout the testing period. This directly validates the design hypothesis: the negatively charged microenvironment generated by the Fe-Sn electronic interaction had done its job, keeping the poison away from the active center even as the catalyst worked hard for tens of thousands of cycles.

“For seawater batteries, activity alone is not enough,” said Peng Rao, the corresponding author of the study. “The catalyst also needs to drive oxygen conversion efficiently while resisting chloride-induced poisoning. The Fe-Sn dual-site structure gives us a way to combine these two functions at the atomic level.” The quote captures the central lesson of the work: in marine electrochemistry, selectivity against chloride is not an optional extra but a design requirement on par with activity itself.

The practical payoff was demonstrated when the catalyst was assembled into flow-type seawater air batteries. Devices built with the FeSn dual single-atom catalyst reached a peak power density of 255.6 milliwatts per square centimeter, higher than comparable cells based on platinum-on-carbon or the iron-only single-atom catalyst, and operated stably for more than 500 hours under the reported testing conditions. That combination of high power and long endurance in a realistic seawater-fed architecture suggests the material is ready to be taken seriously for marine energy systems rather than remaining a laboratory curiosity.

Beyond the immediate application, the study positions p-d orbital engineering as a general strategy for designing electrocatalysts that must simultaneously deliver high activity and resist chloride attack. Many reactions of interest in seawater electrochemistry, from oxygen evolution to chlorine-tolerant hydrogen production, face the same fundamental challenge of selective chemistry in an ionically aggressive medium. If pairing active transition-metal sites with judiciously chosen p-block partners proves general, the design principle demonstrated here could extend well beyond iron and tin, and well beyond oxygen reduction.

The research, published in Science Bulletin, arrives at a moment of growing investment in ocean-based energy infrastructure. Offshore wind farms, autonomous underwater systems and remote marine sensors all need durable storage, and seawater batteries are among the few options whose electrolyte comes free with the deployment site. By showing that a simple atomic partnership, one iron atom and one tin atom held in place on a carbon support, can defuse the corrosive chemistry of the ocean while accelerating the very reaction the battery depends on, the Hainan University team has moved the field a meaningful step closer to seawater batteries that survive, and thrive, in the environment they are built to harness.

Subject of Research: Development of an iron-tin dual single-atom catalyst using p-d orbital hybridization to improve oxygen reduction activity and chloride resistance in seawater batteries

Article Title: How can seawater batteries survive chloride corrosion?

Article References: How can seawater batteries survive chloride corrosion?. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: seawater batteries, oxygen reduction reaction, dual single-atom catalyst, chloride corrosion, p-d orbital hybridization, iron-tin catalyst, electrocatalysis, alkaline electrolyte, marine energy storage, density functional theory, nitrogen-doped carbon, air cathode

Every chemical transformation is governed by kinetic barriers, energy thresholds that must be overcome for reactants to convert into products. These barriers often necessitate high energy input, limiting the sustainability and economic viability of industrial reactions. Traditionally, catalysts—substances that accelerate chemical reactions without themselves being consumed—have mitigated these challenges by providing alternate reaction pathways. Metallic catalysts, especially those comprised of rare or precious metals, have been the mainstay in fostering such reactions due to their unique surface properties and electronic structures.

The ETH Zurich team’s breakthrough hinges on engineering a catalyst at the atomic scale. Unlike conventional catalysts that rely on metal nanoparticles composed of thousands of atoms, this new approach harnesses the catalytic potential of individual indium atoms. Each atom behaves as an isolated active site, maximizing the utility of the metal and providing far-reaching implications for resource efficiency, especially with scarce or expensive metals. The method constitutes a paradigm shift from the often empirical “hit or miss” strategies used in catalyst development, enabling a more rational and predictive design process.

Methanol serves as a cornerstone chemical in global industry, underpinning the production of fuels, plastics, solvents, and a broad portfolio of materials. Professor Javier Pérez-Ramírez, a leading figure in catalysis research and head of the ETH Zurich group, refers to methanol as the “Swiss army knife of chemistry.” Its versatility makes it a pivotal molecule for transitioning from fossil-based feedstocks toward more sustainable, renewable routes of chemical synthesis. The ability to synthesize methanol from CO₂ directly addresses the urgent need to recycle a major greenhouse gas, converting a climate liability into a valuable product.

A defining feature of this new catalytic system is the single-atom architecture, wherein indium atoms are dispersed sparsely and anchored on the surface of a uniquely structured hafnium oxide substrate. This support material was meticulously engineered to not only stabilize the isolated atoms under demanding reaction conditions but also to facilitate their interaction with reactant molecules. The singular atom configuration ensures that every indium atom is catalytically active—a stark contrast to traditional catalysts where the majority of metal atoms within nanoparticles remain chemically inert.

To achieve this finely dispersed state, the research team developed novel synthetic pathways. One particularly effective method involved combusting precursor materials in flames at extreme temperatures ranging from 2,000 to 3,000 degrees Celsius, followed by rapid quenching. Such conditions prevent the aggregation of indium atoms into larger clusters, instead “locking” individual atoms onto the hafnium oxide surface. This high-temperature synthesis also imparts remarkable thermal stability to the catalyst, allowing it to endure the rigorous conditions characteristic of methanol synthesis—temperatures upwards of 300°C and pressures reaching 50 atmospheres.

The ability of this catalyst to remain stable and active under such extreme conditions addresses a long-standing challenge in heterogeneous catalysis. Conventional single-atom catalysts often suffer from sintering, where atoms migrate and coalesce into inactive clusters, diminishing catalytic performance over time. By leveraging the robustness of hafnium oxide as a support, the ETH team’s catalyst combines single-atom precision with exceptional durability, opening avenues for industrial adaptation.

Analyzing the reaction mechanisms underpinning methanol synthesis on this catalyst has also been revolutionized. Unlike nanoparticle catalysts, where signals from inactive internal atoms obfuscate mechanistic insights, the isolated atom format permits more accurate and less noisy characterization techniques. This clarity has enabled researchers to dissect the role of metal-support interactions and understand how the electronic environment of single indium atoms facilitates CO₂ activation and hydrogenation, shedding light on the fundamental steps that govern catalytic performance.

Indium’s catalytic potential has been recognized before, albeit in nanoparticulate form, used over the past decade in various methanol synthesis contexts. The ETH Zurich study conclusively demonstrates the superiority of single-atom indium species supported on hafnia, achieving higher methanol yields and selectivity compared to their nanoparticle counterparts. This evidence supports the notion that catalysts can unlock novel reaction pathways or reduce activation energies when metals assume isolated atomic states.

The interdisciplinary effort behind this research underlines the importance of collaboration spanning chemistry, materials science, and chemical engineering. By combining synthetic innovations, rigorous characterization, and detailed mechanistic studies, the ETH research collective has not only engineered a high-performance CO₂ conversion catalyst but also established a foundational strategy applicable to a wide range of catalytic transformations.

Beyond environmental benefits, the increased efficiency and metal atom utilization present a pathway toward the economic viability of catalytic processes reliant on precious or rare metals. This atomically precise paradigm may lead to downsizing the quantity of expensive catalysts required, thereby fostering sustainable industrial practices. Moreover, the catalyst’s robust performance under industrially relevant conditions indicates readiness for scale-up and integration into existing chemical production infrastructure.

This achievement represents a crucial milestone in the quest for carbon-neutral chemical manufacturing. By transforming CO₂ from a problematic emission into a core feedstock for key industrial chemicals, the ETH Zurich team’s catalyst embodies the potential of nanotechnology and atomic-level engineering to solve pressing environmental challenges. The convergence of fundamental science and technological innovation charts a promising course for future methanol production and broader applications in green chemistry.

In summary, the development of single-atom indium catalysts supported on hafnium oxide not only offers a groundbreaking solution to enhance methanol synthesis from greenhouse gases but also establishes a versatile platform for rational catalyst design. With sustainability at its heart and scalability in sight, this research paves the way toward a more efficient, environmentally friendly, and economically feasible chemical industry.

Subject of Research: Catalysis, Single-atom catalysis, Green chemistry, Carbon dioxide conversion, Methanol synthesis.

Article Title: Single atoms of indium on hafnia enable superior CO2-based methanol synthesis.

News Publication Date: 2 March 2026.

Web References: DOI:10.1038/s41565-026-02135-y

Image Credits: Graphic by Constance Ko / ETH Zurich.

Keywords

Single-atom catalyst, Indium, Hafnium oxide, Methanol synthesis, CO2 conversion, Green chemistry, Sustainable catalysis, Nanotechnology, Catalyst design, Carbon neutrality, Industrial chemistry, Renewable fuels.

At the heart of the new discovery lies the strategic positioning of two single-atom catalytic centers that function in concert to manipulate electronic structures within the immediate reaction environment. These dual sites generate charge-polarized regions that significantly lower the activation barrier for C-H bond cleavage. Unlike traditional catalysts that rely on bulk metal surfaces or homogeneous molecular catalysts, this dual single-atom configuration harnesses atomic-scale precision, enabling more efficient and selective activation pathways.

The study, brilliantly conducted by Chen, Zhou, Lyu, and their colleagues, uncovers how the electronic interplay between adjacent single-atom sites intensifies local charge polarization. This phenomenon effectively polarizes the methane molecule itself, weakening the C-H bond by redistributing electron density. Such polarization reduces the energy input required to break the bond, opening the door to catalytic processes that proceed at lower temperatures and with higher specificity than previously attainable.

This advancement transcends mere catalytic efficiency; it introduces a conceptual shift in how chemists understand and design catalysts for hydrocarbon transformations. The dual single-atom sites act as a cooperative duo, each atom fine-tuned to stabilize reaction intermediates and transition states through synergistic electronic effects. By engineering the catalyst at the atomic level, the researchers have paved the way for bespoke catalysts tailored for specific bond activations across a spectrum of challenging substrates.

Moreover, the formation of these charge-polarized regions is not simply a passive effect but can be dynamically modulated by external stimuli such as electric fields or ligand environments. This tunability enhances the versatility of the catalyst system, suggesting potential for adaptive catalytic frameworks that respond to changing reaction parameters or feedstock compositions in real-time. Such adaptability could be invaluable for industrial applications, where feedstock quality and reaction conditions often fluctuate.

The implications of this work extend deeply into the realm of sustainable energy and chemical manufacturing. Efficient C-H bond activation in methane can transform natural gas—a widely available yet underutilized resource—into value-added chemicals and fuels with reduced environmental impact. Traditional methane conversion techniques, such as steam reforming, require high temperatures and suffer from carbon emissions and catalyst deactivation. The new dual single-atom catalyst platform promises a greener, more energy-efficient alternative by enabling selective activation pathways under milder conditions.

From a materials science perspective, the synthesis and stabilization of these dual single-atom sites represent a formidable challenge overcome by advanced support materials and precise fabrication methodologies. The catalyst design involves anchoring metal atoms onto substrates that provide not only mechanical stability but also electronic environments conducive to charge polarization. This integration highlights a cross-disciplinary triumph, incorporating insights from surface chemistry, nanotechnology, and computational modeling.

Computational studies accompanying the experimental work revealed the nuanced electronic interactions underpinning the observed catalytic phenomena. Density functional theory (DFT) calculations predicted the optimal spacing and electronic properties of the dual sites, guiding the experimental synthesis. These simulations illuminated the charge redistribution patterns that facilitate the weakening of the methane C-H bond, underscoring the power of theory-experiment synergy in contemporary catalyst design.

Kinetic analyses conducted during the study demonstrated significant reductions in activation energy correlated with the presence of dual single-atom sites. This kinetic enhancement translates to faster reaction rates and improved catalyst turnover frequencies. Notably, these improvements were achieved without sacrificing catalyst selectivity or stability, addressing a longstanding trade-off in catalytic methane activation.

Beyond methane, the fundamental insights gleaned from this research are poised to impact the broader field of selective bond activation. The principles of charge polarization at dual atomic sites could be extended to activate other robust chemical bonds, including C-C and C-N bonds, which are critical in the synthesis of pharmaceuticals and complex organic molecules. This strategy may thus unlock new catalytic pathways previously deemed infeasible due to energetic constraints.

The experimental methodologies employed to characterize the catalyst were equally sophisticated. Techniques such as aberration-corrected transmission electron microscopy (AC-TEM) and synchrotron-based X-ray absorption spectroscopy (XAS) provided atomic-level visualization and electronic state information, confirming the presence and dual functionality of the single-atom sites. These cutting-edge tools were essential for validating the structural hypotheses derived from computational models.

Environmental and economic considerations further amplify the significance of this discovery. By enhancing methane activation efficacy, the need for extreme energy inputs diminishes, potentially lowering operational costs and carbon footprints in industrial processes. Additionally, the capacity to use earth-abundant metals in single-atom forms aligns with sustainable resource utilization, circumventing reliance on scarce or toxic elements.

This research also sparks intriguing possibilities for future exploration, including the development of catalysts capable of tandem or cascade reactions. By orchestrating multiple activation and transformation steps at neighboring dual atom centers, chemists might construct complex molecule synthesis pathways within a single catalytic framework, increasing efficiency and reducing waste.

Furthermore, the study invites a reevaluation of existing catalytic paradigms by emphasizing atom-level precision and electronic effect manipulation. It challenges researchers to think beyond traditional bulk catalyst surfaces and embrace the unique opportunities presented by single-atom catalysis combined with cooperative site interactions. Such innovation heralds a new frontier in catalysis research.

In summary, the formation of charge-polarized regions at dual single-atom catalytic sites represents a transformative approach to activating methane’s C-H bonds. This mechanistic insight opens avenues for more sustainable and selective chemical conversions, with broad implications across energy, materials science, and synthetic chemistry. As this field progresses, we may witness a paradigm shift in how catalysts are conceived, designed, and utilized in the quest for greener and more efficient chemical processes.

The work by Chen, Zhou, Lyu, and collaborators stands as a beacon of interdisciplinary collaboration and scientific ingenuity, illustrating the profound impact of atomic-scale control in tackling long-standing chemical challenges. Their contribution not only advances fundamental science but also inspires future innovations aimed at harnessing the full potential of catalytic chemistry in addressing global energy and sustainability goals.

Subject of Research: Activation of methane C-H bonds via charge-polarized regions at dual single-atom catalytic sites.

Article Title: Formation of charge-polarized regions at dual single-atom sites for C-H bond activation in methane.

Article References: Chen, D., Zhou, J., Lyu, W. et al. Formation of charge-polarized regions at dual single-atom sites for C-H bond activation in methane. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69822-1

Image Credits: AI Generated