Electrocatalytic Activity Enhancement on Nitrobenzene Reduction via the p-d Orbital Hybridization from Single-to Dual-Atom Catalysis

Abstract

Aniline (PhNH 2 ) is usually prepared via hydrogenation of nitrobenzene (PhNO 2 ) under the high-temperature and high-pressure. Consequently, the development of PhNO 2 electrocatalytic hydrogenation catalysts with high activity under mild conditions is of great significance for PhNH 2 green preparation and electrochemical energy storage. In this paper, a series of single atom catalysts and corresponding double atom catalysts are designed to explore the electrocatalytic reduction mechanism of PhNO 2 and screen the optimal catalyst. Firstly, 14 types of transition-metal single-atom catalysts (SACs; Co, Cu, Ni, Fe, Pd, Au, Ag, Cd, Ir, Mo, Rh, Mn, Zn, and Cr) were supported on nitrogen-doped graphene to theoretically screen their electrocatalytic PhNO 2 hydrogenation performance by density functional theory (DFT), the Co SAC showed the best catalytic activity and selectivity. Secondly, 10 kinds of N-doped graphene-supported Co-M-N 6 V 4 -G double-atom catalysts [M = Al, Ga, Ge, In, Sn, Sb, Tl, Pb, Bi, Co] were designed to explore the synergistic effect of the diatomic sites. The screened Co-Bi-N 6 V 4 -G catalyst exhibited the best catalytic activity and selectivity by the structure stability, free energy diagrams, limiting voltage and hydrogen evolution reaction. Thirdly, the electronic structure analysis of the doubleatom catalyst shows that the improved performance of the catalyst is due to regulate the medium interaction between nitrobenzene and catalyst by the p-d orbital hybridization of the Co-Bi-N 6 V 4 -G. This study provides a new theoretical method for the design of double-atom catalysts from the atomic orbital level.