Unraveling the Intrinsic Mechanism of High-Performance Two-Dimensional Conjugated Metal–Organic Frameworks for ORR/OER through Theoretical Investigation

Abstract

Developing low-cost and high-performance bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of significance in fuel cells and metal-air batteries. Two-dimensional metal–organic frameworks (MOFs) can be as promising electrocatalysts based on abundant exposed metal sites. Herein, conjugated 2,3,8,9,14,15-hexahydroxyltribenzocyclyne (HHTC) and transition metal (TM = Cr, Mn, Fe, Co, Ni, Cu, Zn) were used to design a sequence of two-dimensional MOFs (TM-HHTC), and their electrocatalytic ORR/OER activities were further investigated by density functional theory. The results demonstrate that Co-HHTC exhibits good structural stability and exceptional electrocatalytic ORR/OER performance with both ultralow overpotentials of 0.21 V, exceeding most reported bifunctional electrocatalysts. Detailed electronic structure calculations show that Co sites have a moderate adsorption interaction with key intermediates, which is conducive to ORR/OER processes. This work reveals the intrinsic mechanism of MOFs for ORR/OER at the atomic level, which provides valuable theoretical insights into the high-performance bifunctional electrocatalysts.