Revealing the primary role of the V4+/V5+ cycle in InVO4 catalysts for promoting the photo-Fenton reaction

Abstract

Surface oxygen and metal defects can promote the performance of photocatalysts significantly, but their role in the activation of hydrogen peroxide (H₂O₂) for pollutant degradation is not clear. Herein, the surface oxygen vacancies (V_O) and vanadium vacancies (V_V: V⁴⁺/V⁵⁺) of InVO₄ catalysts were adjusted using different surfactants. Among them, a cationic surfactant with a hydrophilic head of quaternary ammonium ions facilitated the formation of surface vanadium vacancies (V⁴⁺/V⁵⁺) on the InVO₄ crystal. This V_V-dominated InVO₄ exhibited the optimal degradation rate of rhodamine B and microcystin-LR (MC-LR) with H₂O₂ (0.045 M) at neutral pH under visible-light irradiation, which was ∼8.2-times versus 3.2-times larger than that of the Vo-dominated InVO₄ system. The cycle of V⁴⁺/V⁵⁺ decomposed H₂O₂ to yield hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) continuously, which degraded organic pollutants efficiently. This study provides insights into the primary role of the V⁴⁺/V⁵⁺ cycle in InVO₄ catalysts for promoting the photo-Fenton reaction via adjuration of surfactants.