▎ 摘　　要

Electrochemical nitrogen reduction reaction (NRR) is one of the most promising alternatives to the traditional Haber-Bosch process. Designing efficient electrocatalysts is still challenging. Inspired by the recent experimental and theoretical advances on single-cluster catalysts (SCCs), we systematically investigated the catalytic performance of various triple-transition-metal-atom clusters anchored on nitrogen-doped graphene for NRR through density functional theory (DFT) calculation. Among them, Mn-3-N4, Fe-3-N4, Co-3-N4, and Mo-3-N4 were screened out as electrocatalysis systems composed of non-noble metal with high activity, selectivity, stability, and feasibility. Particularly, the Co-3-N4 possesses the highest activity with a limiting potential of -0.41 V through the enzymatic mechanism. The outstanding performance of Co-3-N4 can be attributed to the unique electronic structure leading to strong it backdonation, which is crucial in effective N-2 activation. This work not only predicts four efficient non-noble metal electrocatalysts for NRR, but also suggest the SCCs can serve as potential candidates for other important electrochemical reactions. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.