Phase-effect of Bi2O3 in photocatalytic degradation of 2-chlorophenol via a preferential dechlorination pathway

Abstract

Photocatalytic preferential dechlorination of high-environmental-risk 2-chlorophenol (2-CP) is highly desired. Although Bi₂O₃ has previously displayed a preferential dechlorination pathway of 2-CP, the phase-effect of Bi₂O₃ remains ambiguous. Here, one dimensional (1D) α- and β-Bi₂O₃ photocatalysts were prepared by using bismuth metal organic framework (CAU-17) microrods as the template, of which β-Bi₂O₃ microrods were obtained via a bicarbonate-induced transformation route and α-Bi₂O₃ microrods were prepared through a direct pyrolysis route. Multi-pronged characterization confirmed that β-Bi₂O₃ microrods have a larger surface area and a narrower band gap compared with α-Bi₂O₃ microrods. As expected, β-Bi₂O₃ microrods showed a 2-fold higher photocatalytic activity for degrading 2-CP under white-light LED irradiation, with higher mineralization than α-Bi₂O₃ microrods. According to liquid chromatography tandem mass spectrometry, radical trapping experiments and ion chromatography, both α-Bi₂O₃ and β-Bi₂O₃ displayed a hole-induced photocatalytic preferential dechlorination of 2-CP, resulting in the conversion of chlorine into chloride ions.