Theoretical study on the mechanism of electrocatalytic nitrogen reduction of ammonia with single-atom catalyst loaded on CN4

Abstract

Electrocatalytic ammonia synthesis is an attractive strategy for low-temperature ammonia production. Designing efficient electrocatalysts with high activity and selectivity for the nitrogen reduction reaction (NRR) remains a significant challenge. In this study, we demonstrate the feasibility of single-atom catalysts (SACs) for NRR using density functional theory (DFT) calculations, focusing on single transition metal (TM) atoms (from Sc to Zn) supported on nitrogen-doped carbon materials (CN₄). The results show that N₂ molecules can be efficiently activated on TMN₄ in an end-on configuration, followed by the distal associative pathway to achieve NRR ammonia synthesis. Moreover, the calculation results of NRR reaction activity for ten TMN₄ SACs reveal that CrN₄ SAC exhibits high NRR activity with a limiting potential of −0.70 eV and greater reaction selectivity over the competing hydrogen evolution reaction (HER). Multiple-level descriptors (ΔG_*N2, Bader charge, charge differential density, ELF, pCOHP, and PDOS) reveal the origin of NRR activity from the perspectives of energy and electronic structure. The dissolution potential and AIMD dynamic calculation further verify its structural stability. This work provides theoretical guidance for the rational design, screening, and development of efficient SACs for the NRR process.