Impact of MOF Coatings and Electrolyte Composition on the Microenvironment of Copper Electrodes for CO Reduction

The electrochemical reduction of CO2 to value-added C2+ products is a promising route for sustainable carbon utilization, but challenges exist in achieving selectivity and efficiency. A direct supply of CO to an electrode surface for CO reduction is an effective way to enhance the selectivity for C2+ products, but strategies are still needed to limit the concentration of water at the electrode interface and hence the hydrogen reduction reaction (HER). In this work, we investigate the impact of metal-organic framework (MOF) coatings and electrolyte composition on the microenvironment at copper electrodes as well as its ability to suppress HER. Using a combination of molecular dynamics (MD) simulations and electrochemical experiments, we examine how NU-901 and ZIF-8 coatings influence solvent structuring, including CO and water coordination at the electrode surface. Experimental results show that MOF-coated copper electrodes exhibit lower Faradaic efficiencies for ethylene and methane production compared to bare copper. NU-901, with larger pores, allows more access to CO and water but favors hydrogen evolution over CO reduction, reducing selectivity for C2+ products. ZIF-8, with its smaller pores and hydrophobicity,1 restricts water coordination but does not improve C2+ formation. MD simulations reveal that MOF coatings regulate the electrolyte structure and coordination of CO and water at the copper surface and that these effects are governed by the pore architecture, solvent-MOF interactions, and the presence of an applied electric field.