insights into correlating CO coverage and Cu-Au alloying with the selectivity of Au NP-decorated CuO nanocubes during the electrocatalytic CO reduction.

Electrochemical reduction of CO (CORR) is an attractive technology to reintegrate the anthropogenic CO back into the carbon cycle driven by a suitable catalyst. This study employs highly efficient multi-carbon (C) producing CuO nanocubes (NCs) decorated with CO-selective Au nanoparticles (NPs) to investigate the correlation between a high CO surface concentration microenvironment and the catalytic performance. Structure, morphology and near-surface composition are studied X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy, high-energy X-ray diffraction as well as quasi X-ray photoelectron spectroscopy. These studies show the continuous evolution of the local structure and chemical environment of our catalysts during reaction conditions. Along with its alloy formation, a CO-rich microenvironment as well as weakened average CO binding on the catalyst surface during CORR is detected. Linking these findings to the catalytic function, a complex compositional interplay between Au and Cu is revealed in which higher Au loadings primarily facilitate CO formation. Nonetheless, the strongest improvement in C formation appears for the lowest Au loadings, suggesting a beneficial role of the Au-Cu atomic interaction for the catalytic function in CORR. This study highlights the importance of site engineering and investigations to unveil the electrocatalyst's adaptations to the reaction conditions, which is a prerequisite to understand its catalytic behavior.