Visible-light-driven photo-Fenton reaction with α-Fe2O3/BiOI at near neutral pH: Boosted photogenerated charge separation, optimum operating parameters and mechanism insight.

The performance of the Photo-Fenton process is still limited by the low conversion rate of Fe3+/Fe2+ under near neutral conditions. We report a α-Fe2O3/BiOI catalyst that enhanced the efficiency of Fe2+ generation. The structure, morphology, chemical composition and chemical states of the catalyst were characterized. The α-Fe2O3/BiOI catalyst exhibited remarkable degradation performance for methyl orange (MO), phenol and tetracycline hydrochloride (TCH). The degradation efficiency of α-Fe2O3/BiOI with an optimum α-Fe2O3 loading was 3 and 10 times higher than those of pristine BiOI and α-Fe2O3, respectively. The excellent degradation performance arose from the synergistic effect of the efficient separation and transfer of photogenerated charge at the α-Fe2O3/BiOI solid-solid interface and the optimized Fenton reaction at the solid-liquid interface. The effects of operating parameters including the H2O2 concentration, solution pH, catalyst concentration and MO concentration on the degradation efficiency were investigated. Electron spin resonance results and reactive oxidation species scavenger experiments indicated that superoxide radicals could be transferred into hydroxide radicals via the activation of H2O2. A possible degradation pathway of TCH is proposed. This strategy provides a new perspective for improving the cyclic ability of Fe3+/Fe2+ over heterogeneous catalysts.