Strain Modulating Spin-Selective Charge Transfer Mechanism To Improve OER Kinetics in 2D Fe₃GeTe₂

Spin-polarized charge transfer plays a critical role in the oxygen evolution reaction (OER), yet its underlying mechanism remains elusive. Here, first-principles calculations reveal that OER on 2D ferromagnetic Fe₃GeTe₂ predominantly follows a dual-site mechanism with cooperative active sites, owing to its substantially reduced overpotential (0.34 V vs 0.80 V for the single-site route) and modest O-O coupling barrier (0.68 eV). Tensile strain further enhances the OER activity of Fe₃GeTe₂, reducing the key O-O coupling barrier to 0.45 eV at 5% strain, maintaining the dual-site mechanism preference. Mechanistic analysis shows that the OER on Fe₃GeTe₂ proceeds through a spin-selective charge transfer process. Unlike the single-site route that requires spin-flip at the rate-determining step, the dual-site mechanism maintains consistent spin alignment throughout all four electron transfers, enabling rapid O-O bond formation. Essentially, tensile strain strengthens the spin polarization of Fe₃GeTe₂ at the Fermi level, promoting electron transfer through favorable spin states and generating highly spin-polarized oxygen intermediates that facilitate spin-triplet O₂ formation. These findings uncover a spin-selective charge transfer mechanism that simultaneously lowers thermodynamic and kinetic barriers, offering fundamental insights for the rational design of spin-polarized OER electrocatalysts.