Spin: an essential factor in advancing the oxygen evolution reaction on 2D Fe-MOF

The oxygen evolution reaction (OER) is a crucial component in oxygen-involving reactions and plays a vital role in developing sustainable energy conversion technologies. However, it still requires developing efficient catalysts that can overcome the sluggish reaction kinetics. Recent studies on oxygen electrocatalysis predominantly focussed on the thermodynamic viewpoint of oxygen adsorption, while the catalytic role of spin remains greatly elusive. In this work, we investigated the impact of spin on the OER performance of a two-dimensional iron-based metal-organic framework (2D Fe-MOF) using spin-polarized first-principles calculations. Our results reveal that the pristine Fe-MOF in the high spin state exhibits electronic properties suitable for an OER electrocatalyst. Even after adsorption, the Fe-MOF preserves its high spin state; such magnetic stability ensures the consistent application of the OER. Moreover, adsorption on a 2D Fe-MOF is spin-dependent. It validates that the spin states can regulate the adsorption strength for the OER. Remarkably, the spin-sensitive 2D Fe-MOF yields a significantly low overpotential of 0.49 V, comparable to precious catalysts. Furthermore, the spin-related charge transfer and orbital interaction originate from the overlapping between the O p_z of the oxygen intermediates and the Fe d_z² of the Fe active site. This reveals that the OER on the Fe-MOF is dependent on the selective spin-orbital. Overall, the spin is inevitable in enhancing the OER process, making our work valuable in the development of MOF catalysts. Our finding enriches the atomistic understanding of the OER in the development of noble-metal-free MOF catalysts.