Structural Design of π-d Conjugated TM B N S (x=2, 3) Monolayer Toward Electrocatalytic Ammonia Synthesis.

Single-atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π-d conjugated TM B N S (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM B N S and III-TM B N S are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM B N S and 4-coordinated III-TM B N S monolayers with different single transition metal atoms were systematically investigated. The results reveal that B N S ligand is an ideal support for TM atoms due to existence of strong TM-S bonds. The 3-coordinated I-V B N S is the best SAC with the low limiting potential (U ) of -0.01 V, excellent stability (E =-0.32 eV, U =0.02 V) and remarkable selectivity characteristics. This work not only provides novel π-d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis.