Two-dimensional conductive metal–organic frameworks as efficient electrocatalysts for oxygen evolution and reduction reactions

Abstract

It is vital to search for efficient and stable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts for the development of metal–air batteries. Herein, we systematically investigated a series of TMN_xO_4−x-HTC (TM = Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt; x = 0–4; HTC = hexatribenzocyclyne) analogs of two-dimensional (2D) electrically conductive metal–organic frameworks (MOFs) as potential electrocatalysts for the OER and ORR by using density functional theory calculations. The calculated results exhibit good thermodynamic and electrochemical stabilities of the designed TMN_xO_4−x-HTC. The OER and ORR catalytic activity of the designed catalyst is governed by the interaction strength between the intermediates and the catalyst, and this interaction can be tuned by adjusting TM atoms and the local coordination number of N/O atoms. CoN₃O₁-HTC is found to be the best OER catalyst with an overpotential η^OER of 0.29 V, and RhN₂O₂-HTC exhibits the lowest ORR overpotential η^ORR of 0.20 V. Importantly, RhO₄-HTC, RhN₂O₂-HTC and CoN₁O₃-HTC are predicted as efficient bifunctional catalysts for the OER and ORR. Moreover, the kinetics simulation verifies the four-electron ORR pathway with high activity and selectivity toward H₂O production. The results not only contribute to designing and searching for efficient OER and ORR electrocatalysts but shed light on the opportunities to explore electrochemical applications based on 2D MOF materials.