Electrochemical CO2 Reduction: Classifying Cu Facets

For CO2 reduction reactions, the Cu catalyst is unique, as compared with other metals, because of its ability to produce a wide range of hydrocarbon and oxygenated products. Previously, we have shown that Cu has the unique property of binding CO* without having H* UPD (underpotential deposited). However, the product distribution from Cu depends highly on the exact nature of the Cu surface. In this work, we investigate a series of Cu facets to understand how they affect the product distribution. Some carbon-carbon (CC)-coupled products are statistically shown to highly correlate, while other CC products correlate with C-1 products. We avoid studying the complex reaction network of the CO2 reduction reaction and focus instead on descriptors for the Cu facet product distribution. The coordination number distribution and the binding energies of the intermediates calculated by density functional theory are investigated as descriptors. The binding energies are close for the Cu facets, and the variation shows that two noncorrelating (orthogonal) binding energies contain up to 70% of the information from the binding energies. Further, structural analysis allows us to uniquely identify the (100)x(110) step sites as specific ethanol-producing sites from the CO2 reduction reaction