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

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 t2g orbitals into Ni3Se4. 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 eg 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.