In the relentless pursuit to combat climate change, the electrochemical conversion of carbon dioxide (CO₂) and carbon monoxide (CO) into value-added, energy-rich multi-carbon products has emerged as a beacon of hope. These processes promise not only to mitigate greenhouse gas emissions but also to create sustainable fuel alternatives that could revolutionize the energy landscape. However, steering the selectivity of these conversions toward desired products remains a formidable challenge. This is primarily because multiple competing reaction pathways coexist at electrochemical interfaces, often leading to a mixture of products and limiting the efficiency of carbon-carbon (C–C) bond formation.
Recent research by Zhang, Raciti, and Hall, published in Nature Chemistry, reveals a fascinating breakthrough in this domain. Their study highlights that the local water environment at the electrode interface—not just the catalyst itself—plays a critical role in dictating the reaction pathway and outcome in CO electroreduction. By tuning the structure of interfacial water using highly concentrated sodium perchlorate (NaClO₄) electrolytes, the authors demonstrate a remarkable enhancement in the rate and selectivity of CO conversion to ethylene (C₂H₄), a high-value, two-carbon product.
One of the intriguing observations in this work is the dramatic increase in CO reduction activity when the NaClO₄ concentration is ramped up from a dilute 0.01 molal to a highly concentrated 10 molal solution. This adjustment yielded an 18-fold increase in the rate of CO electroreduction and pushed the Faradaic efficiency for multi-carbon products to an impressive 91% at a potential of −1.43 V versus the normal hydrogen electrode (NHE). These electrochemical parameters underscore the profound impact that electrolyte concentration exerts, making the electrolyte itself a powerful lever to control catalysis.
.adsslot_wfG6JSsPV1{width:728px !important;height:90px !important;}
@media(max-width:1199px){ .adsslot_wfG6JSsPV1{width:468px !important;height:60px !important;}
}
@media(max-width:767px){ .adsslot_wfG6JSsPV1{width:320px !important;height:50px !important;}
}
ADVERTISEMENT
To unravel the underlying mechanisms behind this phenomenon, the researchers employed temperature-dependent electrochemical measurements alongside surface-enhanced Raman spectroscopy (SERS). This dual approach enabled a nuanced interrogation of both kinetics and molecular-scale interactions at the catalytic interface. Temperature variation allowed the team to extract apparent activation enthalpy and entropy values associated with CO reduction to C₂H₄, offering thermodynamic insights into the reaction’s energetic landscape.
The spectroscopic data yielded particularly compelling clues. As ionic strength increased with rising NaClO₄ concentration, the interfacial water exhibited significant structural changes. Notably, the SERS signatures revealed emerging modes associated with non-hydrogen-bonded water molecules, indicative of a disrupted hydrogen bonding network. This disruption led to a more disordered and dynamic interfacial water layer—that is, an environment markedly different from the highly structured hydrogen-bonded ice-like layers typically observed at lower ionic strengths.
These changes in interfacial water structure were reflected in the apparent activation parameters of the CO reduction reaction. At elevated ionic strengths, the apparent activation entropy increased, suggesting that the reaction proceeding through a more disordered transition state encounters a more favorable entropic landscape. This means that a less rigid hydration shell around reacting species lowers the barrier for C–C coupling events, facilitating ethylene formation more efficiently.
This study not only underscores the vital role of interfacial water in electrocatalysis but also opens new avenues to actively design electrolyte conditions to influence reaction pathways. By moving beyond the conventional focus on catalyst materials and morphologies, this research pivots toward the often overlooked, yet equally crucial, role of the electrolyte’s molecular environment. Such a paradigm shift could unlock simpler, more robust strategies to achieve higher selectivities and rates in electrochemical CO and CO₂ conversion.
Understanding water’s behavior at electrode surfaces has historically posed immense challenges, owing to its dynamic hydrogen bonding and sensitivity to subtle environmental changes. The employment of concentrated NaClO₄ solutions as a tool to manipulate water structure provides a novel experimental platform for controlling these interactions. It allows the decoupling of ion-specific effects from water structuring influences, revealing interfacial entropy as a critical thermodynamic parameter for selective catalysis.
Furthermore, these findings hold significance for the broader field of electrochemical energy conversion beyond CO reduction. Interfacial solvent effects are fundamental in various processes, from hydrogen evolution to oxygen reduction and nitrogen fixation. Insights gleaned here could inspire targeted electrolyte engineering to optimize other complex, multi-electron transformations critical for sustainable chemical synthesis.
Intriguingly, the 91% Faradaic efficiency for multi-carbon products achieved here rivals or exceeds many catalytic benchmark systems, suggesting that interfacial water disorder might be as important as—or even more important than—the catalyst composition itself. The ability to reliably trigger and maintain such disorder at electrode interfaces under reaction conditions could become a cornerstone technique in the design of next-generation electrochemical cells.
Moreover, the pronounced effects observed at 10 molal electrolyte concentration emphasize the often overlooked significance of ionic strength in electrocatalytic performance. High ionic strength can alter not only interfacial water but also electric double-layer structures, local pH values, and ion adsorption dynamics. Each of these factors potentially contributes to the altered reaction kinetics and thermodynamics documented in this work. Teasing apart their relative importance remains a promising direction for future studies.
The utility of surface-enhanced Raman spectroscopy in capturing non-hydrogen-bonded water modes opens new vistas for operando characterization techniques. It allows researchers to visually correlate molecular-scale water structuring with catalytic behaviors in real time, providing a powerful feedback loop for catalyst and electrolyte design. Such in situ diagnostics are critical for deciphering the complex reaction landscapes of multi-electron, multi-step transformations like CO reduction.
This research thus exemplifies how a deeper molecular understanding—here of the solvent environment—can translate into practical improvements in electrocatalysis. It challenges the traditional paradigm that focuses predominantly on solid catalyst surfaces, expanding the focus to the triple phase boundary where reactants, catalyst, and solvent converge. This holistic picture is vital for developing truly efficient and selective electrochemical technologies.
In conclusion, the work by Zhang and colleagues provides compelling evidence that disordered interfacial water layers, driven by high electrolyte ionic strength, significantly enhance CO electroreduction to ethylene by facilitating C–C bond coupling. This novel insight into the interplay between water structure and reaction thermodynamics sets the stage for innovative electrolyte engineering approaches in sustainable fuel synthesis. As the scientific community races to develop viable carbon-neutral technologies, such fundamental advances in understanding interfacial phenomena will be indispensable.
The implications of this study ripple across fields of catalysis, electrochemistry, and environmental science, offering a clear message: the properties of interfacial water—a ubiquitous yet elusive component in electrochemical systems—hold untapped potential to transform the efficiency and selectivity of carbon-based chemical transformations. Embracing this principle may unlock new pathways to mitigating climate change while advancing green chemical manufacturing at scale.
Subject of Research: Electrochemical CO reduction to multi-carbon products enhanced by tuning interfacial water structure using concentrated NaClO₄ electrolytes.
Article Title: Disordered interfacial H₂O promotes electrochemical C–C coupling.
Article References:
Zhang, H., Raciti, D. & Hall, A.S. Disordered interfacial H₂O promotes electrochemical C–C coupling. Nat. Chem. 17, 1161–1168 (2025). https://doi.org/10.1038/s41557-025-01859-z
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41557-025-01859-z
Tags: carbon dioxide conversionClimate Change MitigationCO electroreductiondisordered interfacial waterelectrochemical carbon couplingenergy landscape transformationenhanced CO conversion ratesethylene productionmulti-carbon product synthesisreaction pathway selectivitysodium perchlorate electrolytessustainable fuel alternatives
