Reconstruction of Fe-doped Ni3S2 into NiOOH enabled by low Ru for high-rate alkaline oxygen evolution

Sluggish oxygen evolution reaction (OER) kinetics impede alkaline electrolysis. Here, vertically aligned Ru-decorated, Fe-doped Ni 3 S 2 nanowire arrays on Ni foam (Ru-NFS) are synthesized via a one-step hydrothermal route. Distinct from conventional Ni 3 S 2 →NiOOH systems, we operate in a low-Ru, Fe-co-modulated regime where Ru remains S-ligated and highly dispersed, evidenced by the absence of Ru-Ru scattering in EXAFS. This coordination accelerates NiOOH formation, enhances charge transfer, and mitigates Ru loss, yielding Ru-normalized activity beyond single-modulated controls. In 1.0   M KOH (iR-corrected), Ru-NFS requires only 206 and 245   mV to reach 10 and 100   mA   cm -2 , respectively, and sustains stable operation. Mechanistically, COHP analysis shows that Fe substitution and, more strongly, Ru incorporation progressively weaken Ni-S bonds in the precursor, enabling rapid anodic reconstruction to NiOOH. On the reconstructed surface, DOS/PDOS reveal a d-manifold shifted toward EF with increased states, implying higher hole availability and optimized M-O covalency for coupled proton-electron transfer. DFT-CHE at 1.23   V (RHE) identifies *O→*OOH as the thermodynamic RDS, with ΔG reduced from 0.70   eV (NiOOH) to 0.48   eV (Fe-NiOOH) and 0.38   eV (Ru,Fe-NiOOH). Overall, Ru-Fe co-modulation couples reconstruction control with adsorbate-binding optimization, providing a blueprint for robust high-rate OER anodes.