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

Abstract

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_2g 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 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.