Structural Rule of Heteroatom-Modified Single-Atom Catalysts for CO2 Electroreduction Reaction

Carbon dioxide electroreduction reaction (CO2RR) has emerged as a viable strategy to address pressing energy and environmental challenges. Single-atom catalysts (SACs) are of particular interest for CO2RR due to their maximized atom utilization. The incorporation of heteroatoms as ligands is a common strategy to modify the geometric and electronic structures of metal centers to enhance performance. Here, we employed density functional theory study to investigate nitrogen-coordinated SACs with various heteroatom ligands, and elucidated the structural rule of SACs on CO2RR. The results show that the planar structural SACs exhibit relatively better stabilities than the raised ones, and their stabilities exhibit a volcano-shaped trend as a function of the ligand radius, with both excessively large and small radius compromising stability. Although the raised structural SACs have the better ability to activate CO2 for the tip effect, they also hinder the CO desorption and facilitate the H+ adsorption, leading to relatively poor CO2RR activity and selectivity (vs HER). In contrast, the planar-structured SACs generally show better activity and CO2RR selectivity, where promoting the CO2 activation/hydrogenation step is necessary. This work provides fundamental insights into the structure-dependence of SACs, and offers guidance for designing SACs for CO2RR or other reactions.