Doping‐Vacancy Synergy in Iron Antimony Oxide for Efficient Water Electrolysis

ABSTRACT We demonstrate the electronic structure engineering of iron antimony oxide (FeSbO 4 , FSO) through heteroatom (Ti, Zn) doping and controlled oxygen vacancy formation for efficient electrocatalytic water splitting. Heteroatom incorporation elevates intrinsic electrical conductivity to accelerate charge transfer during the hydrogen evolution reaction (HER). Simultaneously, surface oxygen vacancies polarize the local electronic environment at Fe active sites, optimizing the adsorption energetics of oxygen‐containing intermediates to significantly boost oxygen evolution reaction (OER) performance. Ti‐doped FSO with moderate oxygen vacancies (TFSO 30 ) achieves outstanding HER activity (300 mV at 50 mA/cm 2 , Tafel slope of 119.38 mV/dec) due to vacancy‐induced electronic modulation. In contrast, higher oxygen vacancy concentration (TFSO 60 ) drives superior OER performance (188 mV at 50 mA/cm 2 , Tafel slope of 76.18 mV/dec) compared to IrO 2, primarily driven by charge redistribution and the generation of high‐valence active metal species. Density functional theory (DFT) calculations confirm that Ti doping and oxygen vacancies synergistically tune the electronic structure, promote charge transport, and lower reaction energy barriers to accelerate overall water‐splitting kinetics. Overall, this work highlights Ti‐doped FSO as an efficient, earth‐abundant electrocatalyst and provides useful insights into defect‐engineering strategies for catalytic energy conversion.