High-spin state electron configuration in Mn-doped Ni3Se4 for efficient methanol oxidation

This work demonstrates that Mn doping in Ni 3 Se 4 modulates spin state and electronic structure, significantly enhancing methanol oxidation to formic acid with excellent catalytic efficiency at a high current density. The methanol oxidation reaction (MOR) to formic acid offers a promising alternative to the anodic oxygen evolution reaction (OER) in water electrolysis. However, the development of efficient and cost-effective catalysts remains a primary challenge. In this study, an enhancement in catalytic MOR performance is achieved through the incorporation of Mn atoms with unsaturated t 2 g orbitals into Ni 3 Se 4 . Comprehensive experimental analyses and theoretical calculations reveal that substituting Ni with Mn induces strong electron-withdrawing effects, effectively modulating the local coordination environment of the metal centers. The presence of Mn also elongates Ni–Se(O) bonds, which reduces e g orbital occupancy and modifies the spin state of the material. Electrochemical measurements demonstrate that electrodes based on this optimized material exhibit a high spin state and deliver excellent catalytic activity, achieving a MOR current density up to ∼190 mA cm −2 at 1.6 V. This performance enhancement is attributed to the favorable electronic configuration and reduced reaction energy barriers associated with the high-spin state.