Hydrogen Evolution and Carbon Dioxide Reduction Pathways on Graphitic Carbon Nitride Decorated by Single Atoms of Transition Metals<sup>‡</sup>
Anna Vidal-López, Joan Gassó-Capdevila, Miquel Solà, Albert Poater, Sergio Posada‐Pérez
Abstract
The conversion of carbon dioxide (CO 2 ) into valuable products represents a promising strategy to mitigate CO 2 emissions and enable sustainable energy storage. However, the development of efficient and selective catalysts for the electrocatalytic reduction of CO 2 (CO 2 RR) remains a significant challenge. In this study, we explore the performance of first-row transition metal single atoms anchored on g-C 3 N 4 monolayers as potential catalysts for the CO 2 RR. We employed density functional theory (DFT) calculations to investigate the hydrogen evolution reaction (HER) as a competing pathway to the CO 2 RR. Only the candidates that suppress the HER are promising candidates for the selective CO 2 RR. Our results indicate that Ni 1 /C 3 N 4 emerges as the most promising catalyst due to its relatively moderate-to-high overpotential for the HER and a favorable reaction pathway that favors CO production through the HCOO* intermediate. Despite some challenges, such as the strong Ni–CO interaction hindering CO desorption, Ni 1 /C 3 N 4 presents a viable route for CO 2 RR. Mn and Co single atoms exhibit slighly lower overpotential toward HER, overcoming one of the main limitations to be active and selective for CO 2 RR. Nevertheless, Co 1 /C 3 N 4 shows large energy barriers for CO hydrogenation and HCOOH production, while Mn 1 /C 3 N 4 opens the route for formic acid production. This work highlights the importance of evaluating the HER alongside the CO 2 RR to identify catalysts with optimal selectivity and efficiency.