Enhanced Long‐Term Performance of Sulfides in Oxygen Evolution Reaction by Sulfate Ion‐Assisted Strategy

Abstract Transition metal sulfides (TMS) exhibit significant promise as non‐noble‐metal electrocatalysts for the oxygen evolution reaction (OER) in alkaline environments, notwithstanding their susceptibility to long‐term instability due to the gradual leaching of surface‐reconstructed sulfate ions (SO₄²⁻). In this study, a sulfate ion‐assisted strategy is proposed to stabilize the surface‐reconstructed SO₄²⁻ of FeNiS₂. The findings reveal that SO₄²⁻ experiences considerable loss in KOH due to the infinite concentration gradient of SO₄²⁻ on the surface. Conversely, in K₂SO₄/KOH, this strategy mitigates rapid leaching and preserves the predominant surface‐reconstructed SO₄²⁻, thereby enhancing stability in both accelerated degradation (5000 cycles) and long‐term (≥120 h) tests, with ≈95% current density retained. Furthermore, the optimal concentration of SO₄²⁻ proves to be crucial, as supported by both experimental and theoretical results. This approach offers insights into bolstering the long‐term OER stability of TMS and similar compounds, thereby advancing the prospects for widespread application in electrocatalytic water splitting.