Rational design of a two-dimensional metal–organic framework for high-efficiency bifunctional oxygen electrocatalysis†

Owing to their environmental sustainability, electrocatalytic water splitting and rechargeable metal–air batteries are promising approaches to alleviating fossil fuel overuse and environmental pollution. High-performance bifunctional oxygen evolution/reduction reaction (OER/ORR) catalysts can effectively reduce reaction overpotential, addressing the current challenges of slow reaction rates and large energy loss. Herein, we comparatively investigate the performance of a prospective two-dimensional (2D) metal–organic framework (MOF), named M-HITT (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Re, Os, Ir, Pt, Au), using first-principles calculations. Our results show that transition metal atoms remain stable in M-HITT and interact with the substrate through charge transfer. Notably, Rh-HITT has superior bifunctional OER/ORR activity with overpotentials of 0.28 V and 0.31 V, respectively. Furthermore, volcano maps and contour maps are constructed based on the linear relationship of *OH, *O, and *OOH adsorption energies. Utilizing the d-band center and crystal orbital Hamilton populations (COHPs), the interaction trends of M-HITT are quantitatively delineated. Additionally, a new descriptor φ is proposed to offer a predictive tool for the intrinsic catalytic activity of the OER/ORR, which integrates the d-electron number, first ionization energy, and electronegativity. This work identifies a high-performance catalyst for the electrocatalytic water cycle and rechargeable metal–air batteries while providing guidance for designing efficient bifunctional catalysts.