Computational design of bimetallic TM2@g-C9N4 electrocatalysts for enhanced CO reduction toward C2 products

Electrochemical CO reduction (ECOR) as a potential strategy for producing valuable chemicals and fuels has captured substantial attention. However, the currently available electrocatalysts suffer from poor selectivity and low Faradaic efficiency, limiting their industrial application. Herein, we systematically investigate the potential of homonuclear bimetallic electrocatalysts, TM2@C9N4 (TM = Fe, Co, Ni, and Cu), for the ECOR through extensive density functional theory calculations. Our findings suggest that all four proposed monolayers exhibit exceptional stability, making them highly suitable for experimental synthesis and practical applications. Interestingly, these transition-metal dual atoms anchored on C9N4 monolayers show great potential in facilitating the production of high-value C2 products, such as C2H5OH and C2H4, due to the significantly low limiting potentials (-0.06∼-0.46 V) and small kinetic energy barriers (0.54-1.08 eV) for the CO coupling process. Moreover, with the exception of Ni2@C9N4, these bimetallic catalysts demonstrate the impressive suppression of the competitive hydrogen evolution reaction (HER), leading to a high selectivity for C2 products in ECOR. Our predictions would accelerate the development of high-performance C9N4-based dual-atom catalysts for the ECOR.