(450h) Tailoring the Microenvironment for Electrocatalytic CO2 Reduction: Probing the Effects of Interfacial Structure on Activity and Selectivity on a Model Cu Nanowire Array

The performance of the electrocatalytic CO₂ reduction reaction (CO₂RR) is highly dependent on the microenvironment around the cathode. Despite efforts to optimize the microenvironment by modifying nanostructured catalysts or microporous gas diffusion electrodes, their inherent disorder presents a significant challenge to understanding how interfacial structure arrangement governs the microenvironment for CO₂RR. To this end, we will discuss the fundamental role of activity for CO₂, CO, and H₂O and the interplay with cathode structure.

Here, to develop new insights, we introduce a model system featuring hierarchical Cu nanowire arrays with micro-grooves (NAMs) that synergistically stabilize the micro-wetting state, confine CO*, improve local CO₂ concentration, and tune local pH. Via a combination of confocal microscopy, transport modeling, and electroanalytical methods to probe the microenvironment, we elucidate the interplay between local wetting state, local CO/CO₂ concentration, and local pH, which influence reaction pathways towards multi-carbon products. Consequently, for our model system, the optimized configuration demonstrates a significant increase in electrochemically active surface area (ECSA)-normalized activity by 690%, C₂₊ product selectivity by 72%, and Faradaic efficiency by 36%, compared to hydrophobic Cu foil. We propose that our findings unlock new opportunities to engineer the CO₂RR microenvironment through the rational organization of hierarchical interface materials in gas diffusion electrodes.