Theoretical insights into the catalytic mechanism for the oxygen reduction reaction on M3(hexaiminotriphenylene)2 (M = Ni, Cu)

Abstract

Recently two dimensional (2D) metal–organic frameworks have been successfully used as electrocatalysts, which exhibited a high catalytic activity. Herein, we investigated the catalytic mechanism of the oxygen reduction reaction (ORR) on M₃(hexaiminotriphenylene)₂ (M₃(HITP)₂, M = Ni, Cu) in an acidic medium using the density functional theory (DFT) method. The results indicate that the first electron transfer (ET) to nonadsorbed O₂ is a process of long-range ET on the outer Helmholtz plane (i.e. the ET-OHP mechanism). On the surface of M₃(HITP)₂ (M = Ni, Cu), both the 2e reduction pathway and the 4e reduction pathway are feasible, while the 2e pathway to form H₂O₂ is more favorable. In the several competing reactions for the 4e reduction pathway on M₃(HITP)₂, the favorable path is OOH* → O* + H₂O → OH* → H₂O. Our study provides theoretical guidance for gaining deeper insights into the reaction mechanism of the ORR on M₃(HITP)₂ (M = Ni, Cu) catalysts.