Photoacoustic Spectroscopy of BiOCl Photocatalyst Powder

Photoacoustic spectroscopy (PAS) was used for the first time to investigate the optical properties and photocatalysis reaction of BiOCl powder. The results of PAS measurements showed that the photoacoustic (PA) amplitude increased gradually in the visible light region and the white BiOCl powder became black when the measurements were repeated many times. Further studies showed that the occurrence of ultraviolet (UV) light-induced oxygen vacancies was the reason for the formation of black BiOCl and increasing visible light absorption. PAS also showed that oxygen vacancies only appeared when the white BiOCl powder was irradiated by UV light with a wavelength smaller than the absorption threshold wavelength. The formation of oxygen vacancies under UV irradiation was focused in the initial 0.5 h. Moreover, photochemical reactions of RhB dye absorbed on the BiOCl powder were studied by means of PAS. The results showed that the oxygen vacancy formation and photocatalytic reaction occurred simultaneously under UV excitation.