A New Model of Carbon Nitride as a Substrate to Support Single Metal Atom
Dianhui Pan, Shengwei Deng, Liang Chen, Ziqi Tian
Abstract
Carbon nitrides are commonly employed as substrates to anchor single metal atoms. Numerous theoretical studies have previously characterized these single-atom systems using the pristine g-C 3 N 4 structure, featuring a C 6 N 7 motif. However, the relatively large pores in g-C 3 N 4 may not effectively coordinate with metal cations, resulting in discordance with the coordination environment determined by experimental characterization. In this study, we introduce a novel model denoted as CN-N 4, which preserves the essential g-C 3 N 4 motif, while offering four nitrogen sites for metal binding. Compared with g-C 3 N 4, the binding affinity between the metal and this new substrate model is significantly enhanced, similar to that of a commonly studied nitrogen-doped graphene model (N-gra). Additionally, we have assessed the catalytic performance in various reactions, including the hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO 2 RR), and oxygen reduction reaction (ORR). The CN-N 4 -supported system exhibits activity comparable to that of the corresponding N-gra-supported species. Fe- and Co-centered SACs can be promising catalysts for ORR, and relatively stable Cu- g -C 3 N 4 is active to HER and CO 2 RR, consistent with reported experiments. In addition, V-CN-N 4 and Rh-CN-N 4 are predicted to be candidates to catalyze the HER and ORR, respectively. We suggest that the CN-N 4 model aptly captures the local structure of carbon nitride-based materials with a high coordination number, providing an alternative foundation for investigating the reaction mechanisms of these single-atom catalysts.