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 (Cu_1.0/N₂-GDY) is obtained, with the Cu loading of 1.0 wt%. Cu_1.0/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 Cu_1.0/N₂-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-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.