▎ 摘　　要

The formic acid decomposition (FAD) reaction generates H-2 or CO via two competing pathways. The development of high-efficiency catalysts and clarification of the FAD reaction mechanism are therefore important. Single-atom/single-site catalysts (SACs/SSCs) are attracting considerable attention due to their maximum atomic utilization, considerable cost reductions, and superior potential catalytic activity and selectivity. In this work, we precisely designed PdN3-G and Pd3N3-G to elucidate the FAD reaction mechanism and used density functional theory (DFT) calculations to explain the effects of Pd atoms and Pd-3 clusters. Calculations were performed for four possible FAD reaction pathways. The FAD reaction cannot be achieved completely on the PdN3-G surface because of the high energy barriers. However, Pd3N3-G is more favorable with a rate-determining step energy barrier of 0.55 eV for the carboxyl pathway; the energy barrier for the formate pathway is 1.61 eV. The energy barriers of the two CO pathways are 1.31 and 3.01 eV, respectively. The results indicate that Pd3N3-G is a promising catalyst for FAD reaction and provide a theoretical basis for the rational design of SACs/SSCs for FAD reaction.