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 N2-bidentate (note that N2-bidentate site = N^N-bidentate site; N2 ≠ dinitrogen gas in this work) sites are synthesized. Due to the strong interaction between Cu and the N2-bidentate site, a Cu SAC with isolated undercoordinated Cu-N2 sites (Cu1.0/N2-GDY) is obtained, with the Cu loading of 1.0 wt%. Cu1.0/N2-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 Cu1.0/N2-GDY achieves a mass activity of 53.2 A/mgCu toward CH4 under −1.18 V vs. RHE. In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N2 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-N2 sites toward efficient electrocatalysis.