Revealing the Nature of C-C Coupling Sites on a Cu Surface for CO 2 Reduction.

Electrochemical CO 2 reduction technology plays an important role in reducing CO 2 into valuable chemical fuels. Therein, Cu-based catalysts show superior performance for producing high-value C 2+ products. Here, we illustrate the ascendency of high-index facets of Cu catalysts in producing C 2+ products and find that two kinds of sites favor C-C coupling on the surface. One is prone to adsorb the C-C coupling structure by spanning stepped coppers with different coordination numbers. The other is to embed the structure along two columns of Cu with similar characteristics through O and C adsorbed simultaneously. Within all research surfaces, the coupling energy barrier is lowest on the Cu(911) facet, which is consistent with the experiment. The less charged sites promote the stabilization of the CO-CO structure as determined by charge analysis. Furthermore, our results suggest that the high selectivity for C 2+ products on a Cu surface could significantly come from the contribution of the high-index facet.