Identifying the facet-dependent active sites of Cu2O for selective C-N coupling toward electrocatalytic urea synthesis

Understanding the activity phases and reaction mechanisms at the atomic level is essential for the design of electrocatalysts. Herein we investigate the origin of the facet-dependent activity of model Cu2O catalyst for C-N coupling toward electrocatalytic urea synthesis. It was found that the activity of urea synthesis depends on the crystalline facets of Cu2O. The Cu2O (100) facet exhibits higher urea activity and selectivity than the (110) facet, with an average urea yield of 62.4 mmol·g−1·h−1 at –1.5 V (RHE). By using Raman, UV–vis and XPS techniques, it was observed that Cu+ serves as active sites at (100) face of Cu2O, which promotes C-N coupling through synergistic interaction with Cu0. Furthermore, the combined results of operando ATR-SEIRAS and DFT calculations demonstrate that the Cu-Cu2O (100) facet facilitates electrocatalytic C-N coupling between *CO and *NH intermediates due to the reduced energy barriers of hydrogenated *NO on the Cu-Cu2O (100) facet.