BiFeO3/Bi2Fe4O9 S-scheme heterojunction hollow nanospheres for high-efficiency photocatalytic o-chlorophenol degradation

Fabricating phase-mixed heterojunctions is an effective approach to enhance charge separation for high-efficiency photocatalytic o-chlorophenol degradation. In this study, BiFeO3/Bi2Fe4O9 heterojunction hollow nanospheres were prepared by employing a template-adsorption-calcination method. The S-scheme mechanism of BiFeO3/Bi2Fe4O9 heterojunction was confirmed by means of the Kelvin probe and photoelectrochemical measurement. Compared with bare BiFeO3 and Bi2Fe4O9 nanoparticles, the optimized BFO-700 sample displayed 7.7 and 10.7-fold higher photoactivity under visible-light irradiation, respectively. The promoted photocatalytic activity of BFO-700 could be attributed to the increased light absorption due to the hollow structure, the enhanced charge separation due to the S-scheme mechanism via Fe-O channels, as well as the preferential dechlorination via selective adsorption, according to the results of atmosphere-controlled surface photovoltage and transient photovoltage, electron paramagnetic resonance, theoretical calculation, and in-situ Fourier transform-infrared spectroscopy. With the help of liquid chromatography-mass spectrometry and theoretical calculation, a hole-induced selective dechlorination pathway for photocatalytic degradation of o-chlorophenol was proposed.