Transition Metals Doped into g-C3N4 via N,O Coordination as Efficient Electrocatalysts for the Carbon Dioxide Reduction Reaction

Abstract

The electrochemical carbon dioxide reduction reaction (CO₂RR) is a potential and efficient method that can directly convert CO₂ into high-value-added chemicals under mild conditions. Owing to the exceptionally high activation barriers of CO₂, catalysts play a pivotal role in CO₂RR. In this study, the transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) is doped into g-C₃N₄ with a unique N,O-coordination environment, namely, TM–N₁O₂/g-C₃N₄. Herein, the catalytic performance and reaction mechanism for the CO₂RR on TM–N₁O₂/g-C₃N₄ are systematically investigated by density functional theory methods. Especially, through the calculation of ΔG_*H and ΔG_*COOH/ΔG_*OCHO, the catalysts with preference for the CO₂RR over the hydrogen evolution reaction (HER) are selected for further study. Furthermore, Gibbs free energy computation results of each elementary step for the CO₂RR on these catalysts indicate that Ti–N₁O₂/g-C₃N₄ has significant catalytic activity and selectivity for reducing CO₂ to methanol (CH₃OH) with the limiting potential (U_L) of −0.55 V. Finally, through frontier molecular orbital theory and charge transfer analyses, the introduction of the O atoms illustrates that it is instrumental in regulating the electron distribution of the catalytic active site, thereby improving the catalytic performance. This work provides insight into the design of single-atom catalysts with unique coordination structures for the CO₂RR.