In the quest for sustainable chemical production, electrochemical carbon monoxide (CO) reduction has emerged as a promising pathway to synthesize multi-carbon hydrocarbons and oxygenates using renewable electricity. However, the complexity of this reaction lies in its tendency to generate a broad spectrum of products, diluting its efficiency and complicating downstream processing. Unraveling the molecular-level determinants of selectivity is essential to unlock low-carbon technologies that can effectively compete with fossil-based routes. In a groundbreaking study published in Nature Chemistry, researchers led by Ni, Liang, and Cao have uncovered surprising new insights into the role of alkali metal cations at the electrode–electrolyte interface, demonstrating that smaller alkali metals favor hydrocarbon production through fundamental alterations in intermediate interactions on copper catalysts.
Electrochemical CO reduction to valuable chemicals traditionally suffers from poor selectivity, yielding mixtures of ethylene, ethanol, acetate, and other oxygenates. Previous studies on carbon dioxide electroreduction have established that large alkali metal cations such as cesium and potassium tend to enhance carbon–carbon coupling, favoring ethylene formation. However, this latest work challenges conventional wisdom by revealing that lithium ions, the smallest and most charge-dense alkali cation, actually promote substantially higher ethylene selectivity in CO reduction. This counterintuitive finding opens compelling questions about the interplay between cation size, hydration state, and interfacial chemistry.
To probe these phenomena, the team employed operando Raman spectroscopy, a technique that allows direct observation of catalyst surface interactions under realistic electrochemical conditions. Alongside advanced theoretical simulations, they discovered that hydrated lithium ions accumulated at the copper electrode surface form strong hydrogen bonding networks. These networks modulate the electronic environment and spatial arrangement of key adsorbed intermediates, specifically impacting the oxygen-containing groups bound to carbon atoms. The result is a suppression of hydrogenation pathways typically leading to oxygenates, and a concomitant promotion of hydrodeoxygenation steps that favor hydrocarbon production.
At the molecular level, the interaction of lithium with adsorbed oxygenated intermediates is starkly different from that observed with larger alkali ions. Lithium cations exhibit weaker cation–dipole interactions with oxygen atoms in surface intermediates, diminishing stabilization of oxygenates such as CHCHO*—a critical branching point in product selectivity. This subtle but decisive shift in adsorbate-binding energetics funnels reaction intermediates away from partial oxygenated species and toward full hydrocarbon chains, principally ethylene. The identification of these nuanced cation-specific effects illustrates how intimately electrolyte composition can steer reaction mechanisms in electrochemical CO reduction.
Inspired by this mechanistic understanding, the researchers further innovated by tuning the copper catalyst itself through antimony doping. Introducing antimony into the copper lattice modified the catalyst electronic structure, particularly by reducing copper’s intrinsic affinity for oxygen atoms. This alteration effectively destabilized oxygen-tethered intermediates, which would otherwise preferentially yield oxygenated products. The dual strategy of employing lithium-rich electrolytes in combination with antimony-doped copper created a synergistic effect—enhancing hydrocarbon selectivity while suppressing oxygenates. Such rational catalyst design underpinned significant performance improvements in CO electroreduction.
The team tested these combined innovations in a membrane electrode assembly electrolyser, a scalable platform relevant to industrial applications. At a high current density of 150 milliamperes per square centimeter, they achieved ethylene faradaic efficiencies as high as 79%, representing a striking enhancement over previous benchmarks. Furthermore, the energy efficiency measured reached 39%, indicating favorable conversion of electrical energy into chemical fuel with minimal losses. These performance metrics underscore the practical viability of leveraging cation effects and catalyst modification in tandem for carbon valorization technologies.
This study fundamentally shifts the paradigm of electrolyte engineering in electrochemical CO reduction. While past efforts often emphasized large alkali cations for promoting carbon–carbon coupling, it becomes evident that smaller cations like lithium, when judiciously combined with tailored catalyst surfaces, can selectively channel electrons and protons toward hydrocarbon synthesis. The highlighted hydrogen bonding environments and cation–dipole interactions illuminate atomic-scale control knobs previously underappreciated in the electrolytic conversion arena. Such insights are instrumental for advancing next-generation CO2 and CO electrolysis systems.
The implications extend beyond academic curiosity. The ability to steer electrochemical CO reduction toward hydrocarbons such as ethylene holds promise for sustainable production of plastics, fuels, and chemicals. Ethylene is a cornerstone molecule in the petrochemical industry, conventionally derived from fossil feedstocks with substantial carbon footprints. Electrically powered CO conversion technologies offer a pathway to decarbonize these supply chains, provided that selectivity and efficiency can reach industrially relevant levels. The new cation- and catalyst-based strategies revealed here provide a vital blueprint toward that goal.
Moreover, the integration of operando spectroscopic tools and atomistic simulations sets a new standard for investigating electrocatalytic interfaces in real time. By capturing dynamic molecular interactions under working conditions, researchers can precisely correlate electrolyte composition and catalyst modification with reaction pathways. This informed approach accelerates discovery cycles and directs the rational design of electrocatalysts that maximize desired product formation while minimizing unwanted byproducts. It is a cornerstone advancement in the scientific toolkit for sustainable electrochemistry.
While lithium’s promotion of ethylene in CO reduction contrasts with trends in CO2 reduction, it highlights the complexity and nuance of electrocatalytic systems. The difference springs from the distinct intermediates and proton–electron transfer steps involved in the two reactions, as well as the subtleties of surface adsorption geometries. Decoding these varied pathways helps clarify why strategies effective for one reaction do not straightforwardly translate to another, and guides tailored approaches for each conversion target. In this context, the current work delivers a clarifying lens on alkali cation effects specific to CO electroreduction.
The insights also raise new questions about the interplay between cation hydration shells, interfacial water structures, and catalyst composition. The strong hydrogen bonding networks formed by hydrated lithium ions suggest that electrolyte microenvironments, including water ordering and dynamics, critically influence reaction mechanisms. Manipulating these parameters could offer additional tuning capabilities. The role of doping elements like antimony points to further compositional optimizations in copper and other base metals—opening avenues for customized catalyst platforms with precise oxygen affinity and electronic properties.
In the broader landscape of carbon waste valorization, this work exemplifies how fundamental molecular understanding can unlock practical benefits. Transitioning from CO2 to CO reduction pathways leverages complementary mechanistic pathways and enables integration with industrial gas streams composed predominantly of CO. By aligning electrolyte composition and catalyst design with intrinsic reaction properties, the study charts a promising course toward efficient and selective production of hydrocarbons from sustainable feedstocks powered by renewable energy.
As global efforts intensify to mitigate climate change and reduce reliance on fossil fuels, innovations enabling clean and scalable chemical synthesis remain paramount. The discovery described here, connecting the smallest alkali metals with hydrocarbon selectivity in CO electroreduction—augmented by catalyst doping strategies—breaks new ground. It paves the way for more targeted, energy-efficient electrode designs in electrolyzers that can transform CO waste streams into valuable fuels and materials, thus closing the carbon loop with style and precision.
In conclusion, this pioneering research not only overturns prior assumptions about cation influences in CO and CO2 electrochemistry, but also delivers a compelling case study in combining spectroscopy, simulation, and materials engineering for functional catalysts. The achievement of nearly 80% ethylene faradaic efficiency in an industrially relevant setting marks a significant milestone. The nuanced understanding of how small alkali cations, specifically lithium, modulate interfacial interactions to direct selectivity towards hydrocarbons rather than oxygenates represents a quantum leap for sustainable electrocatalysis and carbon management technologies worldwide. As the field evolves, these insights will doubtless inspire further advances in engineering interfaces and catalysts to meet the global energy transition challenge.
Subject of Research: Electrochemical CO reduction to hydrocarbons enabled by alkali cation and catalyst design.
Article Title: Small alkali cations direct CO electroreduction to hydrocarbons rather than oxygenates
Article References:
Ni, W., Liang, Y., Cao, Y. et al. Small alkali cations direct CO electroreduction to hydrocarbons rather than oxygenates. Nat. Chem. (2026). https://doi.org/10.1038/s41557-025-02061-x
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41557-025-02061-x
Keywords: Electrochemical CO reduction, alkali cations, lithium, copper catalyst, antimony doping, hydrocarbon selectivity, ethylene production, operando Raman spectroscopy, hydrogen bonding, cation–dipole interaction, hydrodeoxygenation, membrane electrode assembly electrolyser, energy efficiency, faradaic efficiency, catalyst design.
