Monodispersed Cu sites assembled on ultrathin 2D C3N4 for efficient electrocatalytic CO2 methanation

Electrocatalytic CO2 reduction (ECO2R) to methane is a promising technology that could effectively realize carbon resource integration and energy recycling. Currently, Cu-based catalysts are the most effective catalysts for this process, and a long-term goal of high selectivity and high stability still remains elusive. In this study, a controllable and multistep solid-state pyrolysis route is implemented to successfully introduce atomically dispersed Cu sites (Cu SA) into the two-dimensional carbon nitride (2D C3N4) matrices. The active site density and morphology structure of the Cu SA-2D C3N4 catalyst could be precisely controlled by adjusting the calcination process. Through the strategic combination of an ultrathin 2D structure and uniformly dispersed active sites, the Cu SA-2D C3N4 maximizes the exposure of active sites while suppressing competitive C-C coupling reactions. Ultimately, the optimized Cu SA-2D C3N4-30 exhibit a Faradaic efficiency of 62.9 % for CO2-to-CH4 conversion with a partial current density of 172.4 mA cm-2 at -1.68 V vs. RHE. This work demonstrates an advanced Cu-based electrocatalyst that effectively improves the performance of electrocatalytic CO2 methanation.