Unraveling the Missed Heteroatom-Doping Effect in Pyrite FeS2 for Oxygen Evolution Reaction

• • Co doping in FeS2 generates abundant S2− species by disrupting S–S bond symmetry, accelerating surface reconstruction into FeOOH during OER; this lowers the kinetic barrier for active phase formation, which is critical for reducing overpotential in industrial electrolyzers. • • Post-reconstruction, Co atoms remain integrated in the FeOOH lattice, upshifting the d-band center and optimizing adsorption of oxygen intermediates; DFT calculations confirm a lowered energy barrier for OOH* formation, enhancing intrinsic activity. • • The study provides direct spectroscopic evidence (in situ Raman) linking dopant-induced structural changes to catalytic performance, offering a mechanistic framework for designing pre-catalysts that dynamically transform into active phases. • • The dual functionality of Co dopants—promoting reconstruction and modulating the active phase—addresses the bottleneck of slow kinetics and structural instability in Fe-based OER catalysts, potentially enabling lower overpotentials (ca. 400 mV) and improved durability for large-scale hydrogen production.