Pressure dependence in aqueous-based electrochemical CO2 reduction

Electrochemical CO2 reduction (CO2R) is an approach to closing the carbon cycle for chemical synthesis. To date, the field has focused on the electrolysis of ambient pressure CO2. However, industrial CO2 is pressurized-in capture, transport and storage-and is often in dissolved form. Here, we find that pressurization to 50 bar steers CO2R pathways toward formate, something seen across widely-employed CO2R catalysts. By developing operando methods compatible with high pressures, including quantitative operando Raman spectroscopy, we link the high formate selectivity to increased CO2 coverage on the cathode surface. The interplay of theory and experiments validates the mechanism, and guides us to functionalize the surface of a Cu cathode with a proton-resistant layer to further the pressure-mediated selectivity effect. This work illustrates the value of industrial CO2 sources as the starting feedstock for sustainable chemical synthesis. Electroreduction of pressurized CO2 to chemicals has great potential but remains underexplored. Here, the authors show that increased CO2 coverage under high pressures alters product selectivity. Guided by the results, a proton-resistant Cu/polypyrrole electrode is designed for enhanced CO2 conversion.

Automated summary

Electrochemical CO2 reduction (CO2R) is a method to close the carbon cycle for chemical synthesis. The research has mainly focused on ambient pressure CO2, but industrial CO2 is usually pressurized and in dissolved form. By studying the effects of pressure on CO2R, the researchers found that higher pressure leads to increased formate selectivity. They further enhanced this pressure-mediated effect by functionalizing the surface of a Cu cathode with a proton-resistant layer. This work highlights the potential of using industrial CO2 as a feedstock for sustainable chemical synthesis.