The Research Of Microstructural Regulation, Mechanism And Extending The Response To Visible Light In BiOCl Semiconductor

Photo-generated electron-hole (e--h+) pairs are fundamentally active species in photocatalytic reactions and a good separation of the charge carriers can remarkably boost the overall photocatalytic efficiency. It has been demonstrated that anistropic shaped particles could retard the fast recombination of e--h+ pairs owing to their intrinsic geometric and electronic properties. Additionally, there exists the PTO of photo-generated electron and hole in different crystal facets due to the subtle distinction of coupled facets, which benefits the separation of charge carriers. Therefore, a comprehensive and in-depth understanding of the facet-oriented separation of charge carriers will evidently contribute to the fabrication of highly efficient photocatalyst. In addition, the separation of photo-generated carriers is also able to be enhanced by designing the suitable heterojunctions. However, their deficient combination of the semiconductors is the major problem of the traditional method. Hence, a new prepared method needs to be sought for achieving a higher efficacy.Owning to its unique unique structures and electronic band structures, BiOCl (BOC) has attracted much interest of research in photocatalytic areas, especially for its property related with different facets. However, a clear role of different facets in photocatalytic process still remains elusive. Moreover, the wide band gap holds back its application on large scale, as BOC is only responsive to ultraviolet light. Herein, three aspects were conducted in this work to solve the above problems. Firstly, with Au NPs loaded on different facets of BOC by chemical reduction method (C.D.) and photoreduction method (P.D.), their photocatalytic performances were studied under UV irradiation for exploring the preferred transfer orientation (PTO) of photogenerated electron-hole pairs. Secondly, by loading Au on BOC with exposed (001) and (010) facets in chemical reduction method, we successfully extend the response of the wide gap semiconductor into visible light region, due to the surface plasmon resonance (SPR) effect of Au NPs. This present work contributes to getting a deeper sight of the relationship between specific facets and photocatalytic performance, together with a further understanding of facet-induced SPR effect. Lastly, Bi3O4Cl/BiOCl heterojunctions were prepared by suit synthesis method and traditional method. The performance of the as-prepared Bi3O4Cl/BiOCl was studied under visible light irradiation and the reason of different activities was also considered in this work.The main results and conclusions were shown as follows.Firstly, Au NPs were deposited randomly onto the surface of the samples by chemical reduction method (C.D.), while Au NPs were deposited selectively on (001) facet by photoreduction method (P.D.). When loaded with Au NPs by chemical reduction method, the activity of BOC-001 sample was promoted whereas the BOC-010 one showed an obvious decline. For Au/BOC (P.D.) samples, the photocatalytic performances are both enhanced compared with pure BOC samples. Based on the analysis of the valence band spectra and the investigated the active species in the reaction process, it was demonstrated that electrons and holes will transfer spontaneously toward (001) and (010) facet, respectively.Secondly, this work successfully extends wide gap semiconductor BOC with the visible light response, due to the SPR effect of Au NPs. O2-- radical was regarded as the main active species in this system combining with the atmosphere investigation. Although the Diffuse-reflectance spectra (DRS) analyses impart that the loading amount as well as an average particle size of the Au loaded samples is of resemblance, the facet-induced SPR effects were different. Based on the analyses of atomic model and the binding energy of Bi 4f, the results stated that Au/BOC-010 sample exhibiting higher photocatalytic performance was contributed to the unique open channel structure and stronger interfacial interaction.Lastly, Bi3O4Cl/BiOCl (B3O4C/BOC) heterojunction promoted the photocatalytic activity remarkablely compared with bare BOC under visible light irradiation by suit synthesis method. In comparison with traditional method, B3O4C/BOC prepared by one-step method showed a higher activity, which could attribute to the intimate contact resulting in a good separation of charge carriers.This work evidently helps us understand the intrinsic property of BOC from the perspective of atomic level and the discrepancy of facet-induced SPR effect, In addition, the response of BOC was extended to visible light region after preparing the heterojunction of B3O4C/BOC. Their performances of samples prepared by two methods were compared firstly, and the reason of their different activities was also considered. The results of this study are of some reference value for the investigators for designing photocatalyst.