Synthesis of rod-like PANI/α-Fe2O3 composite catalysts with excellent photo-Fenton catalytic performance

Abstract

In order to synthesize α-Fe₂O₃ with improved surface conductivity for photo-Fenton catalysts, polyaniline (PANI)/α-Fe₂O₃ heterojunction composite catalysts (FP) were prepared using a simple non-in situ polymerization method, in which the aniline monomer is mixed with porous rod-like α-Fe₂O₃ obtained from rod-like β-FeOOH precursors. The effects of annealing temperatures on α-Fe₂O₃ and the molar ratio of the aniline monomer-to-α-Fe₂O₃ on FP were investigated by the removal of methylene blue (MB) under visible light Fenton conditions. The results showed that α-Fe₂O₃ annealed at 500 °C (F(_T2)) exhibits the highest removal activity of MB among the α-Fe₂O₃ series, and when the molar ratio of the aniline monomer-to-F(_T2) is 2 : 1, the sample (FP-3) removed 99% of MB within 20 min, which demonstrated that the visible light irradiation could promote the removal of MB by PANI/α-Fe₂O₃. The enhanced MB removal activity was attributed to the introduction of PANI into α-Fe₂O₃ constructing type-II heterojunctions, improving the surface conductivity and photogenerating the e⁻–h⁺ separation efficiency of α-Fe₂O₃ under photo-Fenton conditions, in which the cycling between Fe(II) and Fe(III) was accelerated by visible light in the FP-3 system. The hydroxyl radical (˙OH) and the cavity radical (h⁺) are the main reactive species in the photo-Fenton experiment as demonstrated using free radical quenching experiments and electron spin resonance tests. In addition, the FP-3 composite catalyst showed relatively good cycling performance.