Cu Single-Atom Electrocatalyst on Nitrogen-Containing Graphdiyne for CO2 Electroreduction to CH4

Developing Cu single-atom catalysts (SACs) with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO2 reduction reaction and understanding the structure-property relationship. Herein, a new graphdiyne analogue with uniformly distributed N-2-bidentate (note that N-2-bidentate site = N<^>N-bidentate site; N-2 not equal dinitrogen gas in this work) sites are synthesized. Due to the strong interaction between Cu and the N-2-bidentate site, a Cu SAC with isolated undercoordinated Cu-N-2 sites (Cu-1.0/N-2-GDY) is obtained, with the Cu loading of 1.0 wt%. Cu-1.0/N-2-GDY exhibits the highest Faradaic efficiency (FE) of 80.6% for CH4 in electrocatalytic reduction of CO2 at -0.96 V vs. RHE, and the partial current density of CH4 is 160 mA cm(-2). The selectivity for CH4 is maintained above 70% when the total current density is 100 to 300 mA cm(-2). More remarkably, the Cu-1.0/N-2-GDY achieves a mass activity of 53.2 A/mg(Cu) toward CH4 under -1.18 V vs. RHE. In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N-2 sites are more favorable in generating key *COOH and *CHO intermediate than Cu nanoparticle counterparts. This work provides an effective pathway to produce SACs with undercoordinated Metal-N-2 sites toward efficient electrocatalysis. (c) 2024, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.