The catalyst in question belongs to the zinc–chromium oxide family, a workhorse system for high-temperature methanol synthesis and, more recently, for the direct conversion of syngas to light olefins such as ethylene and propylene—the building blocks of plastics. In 2016, the landmark OX/ZEO process demonstrated that metal oxides could steer syngas chemistry away from conventional Fischer–Tropsch distributions toward selectively formed olefins, igniting intense interest in which surface features govern that selectivity. Computational work by Zhi-Pan Liu and Sicong Ma had earlier suggested that dynamic coordination of zinc and chromium cations plays a decisive role, but the identity and location of the active oxygen defects remained unresolved. The new study closes that gap by making the invisible visible.

The central methodological innovation is a site-resolved analytical platform that fuses operando, time-resolved energy-dispersive X-ray absorption spectroscopy with mass spectrometry, transient kinetic analysis, and microcalorimetry. Energy-dispersive X-ray absorption spectroscopy, or EDXAS, acquires full absorption spectra in milliseconds, allowing the researchers to track changes in the chromium and zinc local environments while the catalyst was actually working under realistic syngas feed. By pairing these rapid spectral snapshots with simultaneous product monitoring and then applying transient kinetic analysis—the mathematical dissection of how product signals respond to deliberate perturbations of the feed—the team could correlate specific spectral signatures with specific catalytic functions. Calorimetry added the thermodynamic dimension, measuring the heat released or absorbed as oxygen vacancies formed and were consumed.

Why is such sophistication necessary? Conventional tools for identifying oxygen vacancies, such as X-ray photoelectron spectroscopy, suffer from well-documented ambiguities: the oxygen 1s signal often attributed to vacancies in the 531–532 electron-volt range can arise from hydroxyl groups or other surface species instead, a pitfall highlighted in recent critical analyses of ZnO spectra. Moreover, vacancies exist at vanishingly low concentrations on a heterogeneous surface that may contain terraces, steps, dopants, and metal–oxide junctions all at once. Electron microscopy can image vacancies in exceptional cases, but typically under conditions far removed from working reactors. The new approach sidesteps these limitations by measuring the catalyst under genuine reaction conditions and resolving the vacancy population into distinct site types rather than a single averaged count.

What the team found is strikingly specific. Isolated chromium(III) dopants sitting at the Cr/ZnO interface selectively stabilize a particular class of oxygen vacancy—stoichiometric vacancies located at Zn–O–Cr bridge sites—both thermodynamically and kinetically. In other words, these interfacial positions are the easiest places to remove an oxygen atom, and once removed, the vacancy lingers there preferentially rather than migrating elsewhere. Density functional theory calculations, performed by Liu’s group with global structure searches, rationalize this preference: the chromium cation’s electronic structure compensates the charge and strain associated with vacancy formation, lowering the energetic penalty precisely at the interface. The result is a self-assembled ensemble of Cr–O(v) motifs—chromium cations adjacent to oxygen vacancies—that behave as a distinct chemical species with its own reactivity.

And that reactivity is remarkable. The site-specific Cr–O(v) motifs exhibit exceptionally high activity and selectivity for converting syngas into olefins, outperforming the rest of the surface by a wide margin. Meanwhile, the study assigned a second, complementary role to the interfacial oxygen atoms themselves: they serve as the active sites for propane dehydrogenation, the reverse-type reaction in which hydrogen is stripped from propane to form propylene. This dual assignment is conceptually elegant. At the very same interface, the presence of an oxygen atom enables dehydrogenation chemistry, while its absence enables hydrogenation and C–C coupling chemistry leading to olefins. The catalyst’s selectivity is thus dictated by which of these two interfacial states dominates under a given feed, a balance the researchers could quantify through their transient kinetic framework.

The experimental campaign drew on major synchrotron infrastructure. X-ray absorption measurements were conducted at the BL05U, BL20U, and BL14W beamlines of the Shanghai Synchrotron Radiation Facility, with microscopic infrared measurements performed at the BL06B beamline. The combination of rapid energy-dispersive acquisition with mass spectrometric product detection meant that every fluctuation in catalyst structure could be time-stamped against fluctuations in catalytic output. Microcalorimetry experiments, carried out by Rui Ma and Xiao Kong, anchored the energetic analysis, while Bader charge analysis of the computed models clarified how electron density redistributes when an interfacial oxygen is removed. The optimized atomic coordinates for all computational models were deposited publicly on Figshare, reflecting a commitment to reproducibility that accompanies the paper’s extensive source data.

Beyond the specific zinc–chromium system, the significance of this work lies in its transferable methodology. The pairing of operando transient kinetic analysis with energy-dispersive X-ray absorption spectroscopy constitutes, in the authors’ framing, a platform for tuning surface defect chemistry in oxide catalysts generally. Oxygen vacancies are implicated in an enormous range of transformations: carbon monoxide and carbon dioxide hydrogenation, oxidative dehydrogenation of light alkanes, water–gas shift chemistry, and photocatalytic water splitting, to name a few. In ceria, titania, and countless mixed oxides, the vacancy has been invoked as the active site, the charge reservoir, or the oxygen shuttle—but usually without site-level proof. A method that delivers quantitative, site-resolved vacancy counts under working conditions offers the catalysis community a way to move from correlational arguments to causal ones: to state not merely that vacancies exist, but which vacancies, where, doing what.

The practical implications extend to industrial chemistry. Syngas, produced from coal, natural gas, or biomass gasification, is a foundational feedstock, and routes that bypass energy-intensive intermediate steps to deliver olefins directly carry substantial economic and environmental weight. Knowing that isolated Cr(III) dopants at oxide interfaces nucleate the catalytically potent vacancies gives catalyst designers an actionable blueprint: control the dopant distribution, control the interface density, and thereby control the population of the most active sites. The same logic applies in reverse for propane dehydrogenation, where preserving interfacial oxygen rather than removing it defines the design target. As the chemical industry seeks to electrify and decarbonize, rational defect engineering of mixed-oxide catalysts—guided by operando, site-resolved spectroscopy—may prove one of the most powerful levers available, and this study provides a compelling demonstration of what that lever looks like when it is finally pulled with precision.

Subject of Research: Site-resolved identification of catalytically active oxygen vacancies at Cr/ZnO interfaces during syngas conversion

Article Title: Preferential locations of catalytically active oxygen vacancies at Cr/ZnO interfaces during syngas conversion

Article References: Yang, C., Ma, R., Zhang, C., Kong, X., Ding, B., Li, R., Ma, S., Liu, Z.-P., Cao, Y., Fu, Q., Yang, F., Bao, X., & Zhu, Y. (2026). Preferential locations of catalytically active oxygen vacancies at Cr/ZnO interfaces during syngas conversion. Nature Catalysis. https://doi.org/10.1038/s41929-026-01615-7

Image Credits: AI Generated

DOI: 10.1038/s41929-026-01615-7

Keywords: oxygen vacancies, Cr/ZnO interface, syngas conversion, olefins, heterogeneous catalysis, operando spectroscopy, X-ray absorption spectroscopy, transient kinetic analysis, propane dehydrogenation, zinc–chromium oxide, defect chemistry, microcalorimetry

The material at the heart of the study is a bilayer nickelate, a compound in which pairs of nickel-oxide planes are stacked with a spacing of just a few angstroms. In these structures, each nickel atom sits at the center of an oxygen octahedron, and the electronic states near the Fermi level are dominated by nickel 3d orbitals. Two of these orbitals matter most. The dx2-y2 orbital extends within each plane and governs the in-plane conduction, much as it does in cuprate superconductors. The dz2 orbital, by contrast, points along the crystallographic c axis, out of the plane, and can overlap with the pz orbitals of apical oxygen atoms sitting above and below the nickel. This overlap creates a potential pathway for electrons to hop coherently from one layer to its partner in the bilayer.

Theoretical work had long suggested that this interlayer channel could be crucial. Calculations published since 2023 proposed that pressure-driven changes in the bilayer structure enhance dz2 orbital character at the Fermi level, enabling interlayer pairing mechanisms that range from s-wave states with sign changes between sheets of the Fermi surface to interlayer valence bond scenarios. But theory alone could not settle the matter, because the experiments needed to test these ideas, soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering, are notoriously difficult to perform on superconducting nickelate samples. The materials are chemically sensitive, their surfaces degrade in air, and the superconducting fraction within bulk crystals is often inhomogeneous, making it hard to attribute spectroscopic signatures unambiguously to the superconducting phase.

The Chinese-led collaboration overcame this obstacle with a clever materials engineering strategy. They grew thin films of the bilayer nickelate (La,Pr)3Ni2O7 by pulsed laser deposition and protected them with a capping layer that preserves the delicate oxygen stoichiometry of the buried superconducting layers. Crucially, the team prepared a series of films spanning three distinct electronic ground states: insulating, metallic and superconducting. This controlled family of samples gave the researchers something no single superconducting crystal could provide, namely the ability to track how the electronic structure evolves as the material crosses from one quantum state to another, isolating the features that appear only when superconductivity does.

With the capped films in hand, the researchers deployed the full arsenal of modern synchrotron spectroscopy. X-ray absorption spectroscopy at the oxygen K edge and the nickel L3 edge probed the unoccupied electronic states, revealing the orbital character of the charge carriers. Resonant inelastic X-ray scattering, or RIXS, at the nickel L3 edge then measured the energy and momentum resolved spectrum of orbital excitations and spin excitations, the collective magnetic fluctuations that many theorists believe mediate pairing in unconventional superconductors. Resonant elastic X-ray scattering complemented these measurements by detecting static magnetic order, specifically the spin-density-wave order that competes with superconductivity in these compounds.

The results paint a coherent and strikingly clear multiorbital picture. Across all samples, the in-plane electronic structure is built from itinerant dx2-y2 states, which form the conductive backbone of the material regardless of whether the sample insulates, conducts or superconducts. What separates the superconductors from the rest is the out-of-plane channel. Only in the superconducting films did the spectra show evidence of coherent dz2-pz-dz2 hybridization, meaning that the dz2 orbitals on nickel atoms in adjacent layers, linked through the apical oxygen pz orbitals, merge into well-defined bonding and antibonding bands that straddle the bilayer. In the insulating and metallic samples, this interlayer coherence is absent or incoherent, and the two layers effectively fail to form a unified electronic entity.

The magnetic data reinforce the same conclusion. In the non-superconducting samples, static spin-density-wave order is prominent, indicating that electrons are locked into a periodic magnetic texture that gaps out parts of the Fermi surface and suppresses coherent metallic behavior. As the samples move into the superconducting regime, this static spin order is suppressed, and the spin excitations measured by RIXS become strongly damped, their spectral weight broadening and softening in a manner reminiscent of the paramagnons observed in cuprate superconductors. The coexistence of coherent interlayer hybridization, suppressed static magnetism and heavily damped but persistent spin fluctuations defines the narrow window in which superconductivity emerges, suggesting that magnetic fluctuations surviving the collapse of long-range order may still contribute to the pairing interaction.

Perhaps the most practically important finding concerns the tuning knobs that control the interlayer channel. The researchers found that both oxygen stoichiometry and epitaxial strain, the mechanical distortion imposed on the film by the underlying substrate, directly modulate the strength of the dz2-pz-dz2 hybridization. Oxygen vacancies disrupt the apical oxygen network that mediates the interlayer hopping, while strain alters the geometry of the octahedra and the spacing between layers. Because both parameters tune the same orbital channel, superconductivity in bilayer nickelates occupies only a narrow regime of interlayer coherence, explaining why samples grown or treated slightly differently can show wildly different transport behavior. This insight offers a concrete design rule for future experiments: optimize the apical oxygen environment and the interlayer spacing, and the superconducting fraction and transition temperature should follow.

The broader significance of this work lies in how it positions the nickelates relative to the cuprates. In cuprate superconductors, superconductivity is widely understood through a single-band picture in which doped holes in the dx2-y2 orbital pair through antiferromagnetic fluctuations, with the famous Zhang-Rice singlet capturing the essential physics. The bilayer nickelates refuse to fit into that framework. Their superconductivity requires simultaneous coherence in two orbital channels, an in-plane itinerant channel and an out-of-plane hybridized channel, making them genuinely multiorbital superconductors. This complexity is not a nuisance but an opportunity, because it adds new adjustable degrees of freedom, orbital occupancy, interlayer hopping and Hund’s rule coupling, that have no direct analogue in the cuprates and could in principle be exploited to push transition temperatures higher.

The path forward is now well marked. Thin film growth, already proven capable of ambient-pressure superconductivity in these materials, provides the platform for systematic strain engineering, while oxygen recycling protocols allow fine control of the apical oxygen network. Spectroscopists can now interrogate genuine superconducting samples rather than inferring properties from non-superconducting relatives, and the identification of coherent interlayer hybridization as the superconducting enabler gives theorists a sharp target for microscopic models of the pairing mechanism. If the nickelates continue to follow the trajectory that this study illuminates, the dream of a new family of high-temperature superconductors, one built not on a single orbital but on the quantum coupling of paired atomic planes, looks increasingly within reach.

Subject of Research: The role of interlayer orbital hybridization in superconductivity of bilayer nickelate thin films

Article Title: Interlayer hybridization promotes superconductivity in bilayer nickelates

Article References: Zhang, S., Zhang, M., Luo, Q., Tao, Z., Huang, H.-Y., Weschke, E., Li, K., Channagowdra, G., Li, J., Fu, J., Huang, D.-J., Xie, Y., Lu, Y., & Peng, Y. (2026). Interlayer hybridization promotes superconductivity in bilayer nickelates. Nature Materials. https://doi.org/10.1038/s41563-026-02750-z

Image Credits: AI Generated

DOI: 10.1038/s41563-026-02750-z

Keywords: bilayer nickelates, superconductivity, interlayer hybridization, dz2 orbital, resonant inelastic X-ray scattering, X-ray absorption spectroscopy, spin-density wave, thin films, oxygen stoichiometry, epitaxial strain, multiorbital physics, cuprates

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