"Cu-N" Site-Driven Selectivity Switch for Electrocatalytic CO Reduction.

The comprehensive understanding of the effect of the chemical environment surrounding active sites on the pathway for the electrochemical carbon dioxide reduction reaction (eCORR) is essential for the development of advanced catalysts for large-scale applications. Based on a series of model catalysts engineered by the coordination of copper ions with various isomers of phenylenediamine [i.e., -phenylenediamine (PD), -phenylenediamine (PD), and -phenylenediamine (PD)] featuring two amino groups in -, -, and -positions, the steric effects could significantly govern the selectivity of the "Cu-N" sites for eCORR. It was found the steric distance between adjacent copper and nitrogen active sites in Cu-PD enhanced the C-C coupling of the *COOH intermediate, thereby resulting in increased selectivity for CH production. In contrast, the weak van der Waals interactions arising from steric electrostatic effects surrounding the *CHO intermediate on Cu-PD facilitated subsequent hydrogenation, leading to the preferential synthesis of CH. However, Cu-PD exhibited diminished eCORR activity due to a higher free energy associated with the rate-determining step, which primarily led to the formation of H. This study underscores the significant role of a steric effect-driven selectivity switch for eCORR.