Photo-switchable In(III)-to-In(I) site on oxygen vacancy-laden BiOCl surface for selective degradation of monocyclic aromatic compounds

Enrichment of OVs on oxide semiconductors is an effective strategy to promote their photocatalytic performances but limited by the maximum concentration allowed by lattice thermodynamics. Herein, we report that an In(I) doping strategy, realized by an UV light-induced reduction of a sluggish In(III) precursor, can promote OVs-laden BiOCl by up to 6.5 times for the visible-light sodium pentachlorophenate (PCPNa) degradation. The photocatalysis mechanism study highlighted the In(I) site as an electron transfer site could reduce PCPNa directly, related to the In(I) induced more negative conduction band and faster transfer of electron. Moreover, several monocyclic aromatic organic compounds (AOC) exhibited degradation selectivity over In(I) doped OVs-laden BiOCl (BOVs-In) by an electron reduction path, PCPNa with the lowest negative charge density on the benzene ring has been degraded fastest. Differently, the doped In(I) in BOVs-In mainly triggered the multiring Rhodamine B degradation by promoting the O2− generation not the directly electron reduction path. The electron transfer ability, band structure, and the free energy of O2 activation over BOVs-In were confirmed by TPV spectra, EPR spectra and DFT calculation. This study illustrates an In(I) doping strategy to couple with OVs engineering for champion photoactivity of BiOCl for AOC degradation under visible light irradiation.