Insights into the mechanism for the catalytic transfer hydrogenation of nitrobenzene to azobenzene on Au (1 0 0) surface under alkaline condition

Abstract

Azobenzene is very crucial in both academic and industrial research, and can be prepared through the catalytic transfer hydrogenation of nitrobenzene with gold catalyst; however systematic and detailed reaction mechanism has not been reported. In this work, the whole process of catalytic transfer hydrogenation of nitrobenzene on Au (100) surface under alkaline condition was systematically simulated using CP2K. The research results show that PhNO* is the most important intermediate, and the N-N coupling step is realized by the self-coupling of PhNO*. The whole reaction process and the intermediates have been identified as: 2 PhNO2* → 2 PhNO* → Ph(O)N═N(O)Ph* → Ph(O)N═NPh* → PhN═NPh*. The breaking of the first N-O bond of Ph(O)N═N(O)Ph* with H-assistance yielding Ph(O)N═NPh* has the greatest activation energy (0.57 eV), showing that it is the rate-determining step of overall reaction. Our findings provide theoretical support for the catalytic transfer hydrogenation of nitrobenzene to azobenzene at the atomic and molecular levels, which will provide rational strategies for further design of catalysts with high activity and selectivity.