Exceptional visible-light photoelectrocatalytic activity of In2O3/In2S3/CdS ternary stereoscopic porous heterostructure film for the degradation of persistent 4-fluoro-3-methylphenol

In this work, In2O3/In2S3/CdS ternary stereoscopic porous heterostructure films were successfully fabricated via consecutive in situ ionic exchange reactions to degrade persistent 4-Fluoro-3-methylphenol through photoelectrocatalytic process. The optimized In2O3/In2S3/CdS ternary stereoscopic porous heterostructure film electrode showed much higher photoelectrocatalytic efficiency than the In2O3 and In2O3/In2S3 films. The resulting degradation reaction constant is about 3 and 2 times higher than that on In2O3 and binary In2O3/In2S3 films, respectively. The extraordinary higher degradation and mineralization efficiencies of the In2O3/In2S3/CdS composite film electrode come from the synergy of ternary components in the stereoscopic porous heterostructure. The existence of double type-II band alignment with nanosized interfaces in the ternary heterostructure can significantly improve charge transport and electron-hole separation. The stereoscopic porous architechture can greatly enhance visible light utilization and superhydrophilicity, and meanwhile facilitate the mass transport and accessibility of active sites. Ion chromatography, gas chromatography-mass spectrometry, total organic carbon analysis, active species trapping experiment as well as electron spin resonance techniques were employed to probe the degradation and the mineralization processes of 4-Fluoro-3-methylphenol. A unifying photoeletrocatalytic degradation route and mechanism is provided to explain the degradation and the mineralization processes. The generated more superoxide ions and holes promoted the defluorination process and favored the subsequent benzene ring cleavage and mineralization of low molecular weight fragments (e.g. carboxylic acids). This work provides a route to degrade persistent organic pollutants and realize efficient water contamination purification via efficient visible light photoelectrocatalytic process.