Electrochemical carbon dioxide reduction has long been celebrated as one of the most promising routes for turning waste emissions into useful fuels and chemicals, yet the search for catalysts that can perform this conversion efficiently at low energy cost has remained stubbornly difficult. Now, an international team of researchers reports a discovery that could reshape how scientists think about these reactions: positively charged caesium ions, stripped of their surrounding water molecules and trapped in a remarkably specific position on a catalyst surface, can dramatically accelerate CO2 reduction. The work, published in Nature Catalysis, provides the first direct, multimodal spectroscopic evidence that cations influence catalysis not merely through electrostatic attraction but through partially covalent chemical interactions—a finding that challenges decades of conventional assumptions about how electrolytes shape reaction kinetics.
The study focuses on a ligand-modified silver nanocatalyst operating under CO2-reducing conditions, and its central achievement lies in revealing what caesium ions are actually doing at the electrode interface while the reaction is running. Metal cations dissolved in the electrolyte have been known for years to affect the rate and selectivity of CO2 electroreduction, with larger cations such as potassium and caesium often boosting the production of carbon monoxide from CO2. The problem has been that nobody could see precisely how these ions were solvated at the surface, how their hydration shells behaved under the intense electric fields of the electrical double layer, or what kind of bonding, if any, connected them to reaction intermediates. Without that molecular-level picture, explanations for cation effects remained largely speculative, resting on models of electrostatic field stabilization that could not be directly tested.
To penetrate this blind spot, the team combined three complementary techniques that together deliver a view of the interface that no single method could achieve. Surface-sensitive total electron yield X-ray absorption spectroscopy allowed the researchers to probe the local chemical environment of caesium ions within just a few nanometres of the silver surface, a depth range that conventional bulk-sensitive X-ray methods cannot resolve. Surface-enhanced infrared absorption spectroscopy provided a complementary window onto the vibrational signatures of species adsorbed on the catalyst, revealing the configuration of ligands, water molecules and reaction intermediates at the surface under applied potential. These experimental observations were then interpreted through density functional theory calculations, which mapped out the energetics of different solvation structures and bonding arrangements to identify the configurations most consistent with the measured spectra.
What emerged from this multimodal analysis was a strikingly specific picture. Under CO2-reducing potentials, the caesium ions at the interface lose most or all of the water molecules that normally surround them in solution—a process of desolvation that is energetically costly and therefore rarely assumed to occur to a significant extent. These desolvated ions become confined in a nanometre-scale gap between the silver surface and an organic ligand layer that has partially detached from the metal, creating what the authors describe as a sandwich-like confinement geometry. In this confined space, the caesium ions sit close enough to both the surface and the adsorbed CO2-derived intermediates to participate directly in the reaction chemistry rather than simply exerting a long-range electrostatic field.
The catalytic consequences are substantial. The researchers found that the presence of these desolvated, confined caesium ions enables CO2 activation at potentials as high as 0.4 volts versus the reversible hydrogen electrode, a benchmark potential that is remarkably mild for a reaction that typically demands strongly negative voltages. In practical terms, the overpotential required to drive the conversion of CO2 to CO—the key first step in most CO2 electroreduction schemes—was reduced by 250 millivolts compared with an unmodified silver film. Because overpotential translates directly into the electrical energy wasted in driving a reaction, a 250-millivolt reduction represents a meaningful improvement in the energy efficiency of the process, and it was achieved not by redesigning the metal catalyst itself but by engineering the ionic environment around it.
The mechanistic explanation for this enhancement is perhaps the most conceptually significant aspect of the study. Density functional theory calculations revealed that the interactions between the desolvated caesium ions and the CO2-derived intermediates adsorbed on silver are not purely ionic or electrostatic. Instead, they possess a partial covalent character, meaning that the electron density between caesium and the intermediate species is shared to some degree, forming weak but genuine chemical bonds. This partial covalency stabilizes the key reaction intermediates that must form as CO2 is converted into CO, lowering the energy barriers along the reaction pathway. It is this chemical stabilization—rather than the electrostatic field effects that have dominated textbook explanations—that directly accounts for the observed acceleration of catalysis and the lowering of the required potential.
The broader implications of this partial covalent interaction extend well beyond the specific caesium-on-silver system examined here. For decades, the influence of cations on electrocatalytic reactions has been interpreted through the lens of the electrical double layer, in which ions are treated as point charges that modify the local electric field and stabilize charged transition states through Coulombic attraction. The new results demonstrate that this framework is incomplete. When cations shed their hydration shells and approach reaction intermediates closely enough, they can engage in soft chemical interactions that involve actual orbital overlap and electron sharing. Recognizing this opens an entirely new design dimension for electrocatalysis: rather than tuning only the composition and structure of the metal surface, researchers can deliberately engineer the ionic environment—the choice of cation, its solvation behaviour, and the local confinement geometry—to stabilize intermediates chemically and steer reaction pathways.
The experimental methodology itself represents a methodological advance that other laboratories are likely to emulate. Total electron yield X-ray absorption spectroscopy is intrinsically surface-sensitive, but applying it to a working electrochemical interface under gas-diffusion or flow conditions requires considerable technical sophistication. By pairing it with surface-enhanced infrared absorption spectroscopy, which tracks the changing vibrational fingerprints of adsorbates as the potential is swept, and anchoring both in first-principles calculations, the team assembled a self-consistent molecular picture of the interface under genuine operating conditions. This operando, multimodal strategy addresses one of the most persistent challenges in electrochemistry: the difficulty of observing, in real time and at the relevant length scales, the fleeting species that govern catalytic reactions at charged surfaces.
For the field of carbon dioxide utilization, the timing of such advances could hardly be better. Converting CO2 electrochemically into carbon monoxide, which serves as a feedstock for the Fischer-Tropsch synthesis of fuels and for the production of chemicals such as acetic acid and phosgene derivatives, is a cornerstone of emerging carbon-recycling technologies. Silver and its derivatives are among the best-known catalysts for this conversion, and the demonstration that a ligand layer plus a judiciously chosen electrolyte cation can cut the required overpotential by a quarter of a volt suggests that some of the most valuable gains in efficiency may lie in the often-overlooked interface between catalyst and electrolyte. Ligand-modified catalysts, in particular, have attracted growing interest because organic coatings can tune the local chemical microenvironment in ways that bare metals cannot, and this study now shows that they can also create the confinement conditions under which cations desolvate and become chemically active participants in catalysis.
Looking forward, the findings raise a series of questions that will drive the next phase of research. Do other cations—lithium, sodium, potassium, rubidium, or multivalent species—form similar desolvated, confined configurations, and how does the degree of covalency vary across the alkali metal series? Can the ligand layer be designed to systematically tune the strength of cation–intermediate interactions, effectively using the organic coating as a lever to control reaction selectivity between carbon monoxide, formate, and more deeply reduced products such as ethylene and ethanol? And can the principle of desolvated cation catalysis be extended to other electrochemical transformations, including nitrogen reduction, oxygen evolution, and the reduction of nitrate and other pollutant species? Each of these reactions depends critically on the stabilization of charged or polar intermediates at an electrode surface, making them plausible beneficiaries of the same confinement strategy.
The work also carries a cautionary message for how electrochemical data are interpreted. If cations can participate chemically in reactions at the interface, then apparent trends in activity or selectivity attributed to field effects, pH gradients, or surface restructuring may in fact be influenced—or even dominated—by previously invisible cation chemistry. Re-examining established systems with the spectroscopic tools demonstrated in this study could revise the mechanistic understanding of many electrocatalytic reactions, and the authors suggest that their approach offers a general template for such re-examination. In an era when decarbonization demands ever more efficient electrochemical technologies, discovering that a simple ion, once stripped of its water, can act as a genuine chemical partner in catalysis is the kind of insight that reorients an entire field. What was once dismissed as background electrostatics now stands revealed as an active chemical force—one that researchers can harness to lower energy barriers, improve efficiency, and bring CO2 electroreduction closer to practical, large-scale deployment.
Subject of Research: Electrochemical CO2 reduction catalysis; desolvated caesium cations at a ligand-modified silver nanocatalyst interface and their partially covalent interactions with reaction intermediates
Subject of Research: Chemistry
Article Title: Desolvated cations promote CO2 electroreduction through partial covalent interactions
Article References: Shan, Y., Jaugstetter, M., Feijóo, J., Guan, Y., Wang, T., Falling, L. J., Li, J., Ding, H., Sachelarie, A., Fonseca Guzman, M. V., Zhao, X., Kowalski, R. M., Nemšák, S., Guo, J., Sautet, P., Salmeron, M. B., & Yang, P. (2026). Desolvated cations promote CO2 electroreduction through partial covalent interactions. Nature Catalysis. https://doi.org/10.1038/s41929-026-01604-w
Image Credits: AI Generated
DOI: 10.1038/s41929-026-01604-w
Keywords: CO2 electroreduction, caesium cations, desolvation, silver nanocatalyst, ligand-modified surface, total electron yield X-ray absorption spectroscopy, surface-enhanced infrared absorption spectroscopy, density functional theory, partial covalent interactions, overpotential reduction, electrical double layer, carbon monoxide production
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Bethany Barker. (September 4, 2026). Partially covalent desolvated cations boost electrochemical CO2 conversion. Scienmag. https://scienmag.com/partially-covalent-desolvated-cations-boost-electrochemical-co2-conversion/
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