Photocatalytic Degradation Of Sodium Pentachlorophenol On BiOCl Under Visible Light

In recent years, semiconductor photocatalysis shows great prospects in solving environmental pollution. PCP is often used as the model substrates, because of its high toxicity and recalcitrance. Bismuth-based photocatalysts performs good activities for removal of PCP comtaminant, which can add reductive species induced dechlorination process to enhance the degradation efficiency and further reduce intermediates toxicity. Bismuth oxychloride (BiOCl) as a ternary semiconductor material, has excellent performance in photodegradation of organic pollutants, but lack of distinct research about degradation of PCP pollutant under visible light. In this thesis, we chose BiOCl with oxygen vacancies (BOC-OVs) and home-made BiOCl nanodiscs to reveal the crucial roles of oxygen vacancies during the photodegradation of PCP over BOC-OVs, and the functions of surface-complex induced charge transfer for the PCP removal with BiOCl nanodiscs under visible light.First, we demonstrated that surface oxygen vacancies (OVs) on the{001} facets of BiOCl nanosheets were crucial for photocatalytic degradation of pentachlorophenol (PCP) contamination. With PCP intermediates detection, theoretical calculation and radical measurements, we proved that OVs were capable of activating the surface-adsorbed chlorophenol molecules to achieve the hydroxylation process in low oxidation atmosphere under visible light. When increasing the surface OVs concentration of BiOCl nanosheets, more hydroxylation intermediates as Tetrachlorohydroquinone (TCHQ) were generated, which were further oxidated to tetrachloroquinone (TCBQ), favouring the subsequent cleavage of benzene rings. Besides, more surface OVs could also promote the dechlorination process to speed up TCHQ conversion reaction and then facilitate final mineralization of PCP during BiOCl photocatalysis under solar light.Subsequently, we prepared BiOCl nanodiscs photocatalyst by a simply modified methods, and found it had good performance in photocatalytic degradation of pentachlorophenol under visible light. The products were characterised by XRD, SEM, DRS, TEM, HRTEM and nitrogen adsorption. DRS and photocurrent tests revealed that ligand to metal charge transfer process dominated the visible light sensitized photocatalytic mechanism, which extended the light absorption from the UV into the visible range. Moreover, we found that surface-complexes induced charge transfer were common during BiOCl photocatalysis in case that BiOCl nanodiscs were of large surface area and rich surface functional groups.