Earth-Abundant Silicon for Facilitating Water Oxidation over Iron-Based Perovskite Electrocatalyst

Active and affordable electrocatalysts made from Earth-abundant elements are central to water electrolysis involving the oxygen evolution reaction (OER). While nonprecious transition metal-based (Co, Ni, Fe) materials are extensively studied as cost-effective, high-performance alternatives to noble metal-based catalysts, iron-based catalysts with Fe acting as the single active site are rarely investigated due to their intrinsically low reactivity. Here, by taking advantage of the versatility of perovskite structure, metalloid Si, the second most abundant element in Earth's crust, is doped into an Fe-based perovskite oxide (SrFeO_{3− δ}), to obtain SrFe_0.9Si_0.1O_{3− δ} as a highly efficient OER catalyst. Remarkably, SrFe_0.9Si_0.1O_{3− δ} shows an approximately threefold growth in OER activity relative to SrFeO_{3− δ} with a small Tafel slope of 58 mV dec⁻¹, comparing favorably to or even exceeding many Co-/Ni-based perovskite catalysts. This enhancement can be ascribed to a structural transition from tetragonal to cubic symmetry upon Si-doping, which brings about an optimized iron oxidation state, rich oxygen vacancies, and fast charge transfer that are beneficial to the OER catalysis. This work highlights the importance of how incorporating Earth-abundant, nonprecious elements (e.g., Si) into a perovskite oxide structure can be used to create novel materials for the electrochemical water oxidation.