B-C-N-TiO 2 catalysts with intermediate band gap and heterojunction were prepared by sol–gel method. The crystal structure, elemental composition, and absorbance performance were analyzed by XRD, XPS and UV–vis DRS. Due to the formation of the continuous intermediate band gap in the forbidden band, the optical absorption boundary of B-C-N-TiO 2 catalyst extends to 412 nm, which shows different red shift compared with that of TiO 2 (397 nm), N-TiO 2 (400 nm), B-TiO 2 (402 nm) and C-TiO 2 (403 nm).Meanwhile, the B-C-N-TiO 2 catalyst is a uniform spherical solid particle with exposed (101) and (211) planes. The degradation efficiency of B-C-N-TiO 2 catalyst to methylene blue(MB) was up to 97.82% after 3 h under visible light, which shows different degree of improvement compared with that of TiO 2 (34.8%), N-TiO 2 (79.09%), B-TiO 2 (87.82%) and C-TiO 2 (73.19%). B-C-N-TiO 2 has good stability, and there was still more than 95% degradation efficiency after three degradation cycles. It is also revealed that the incorporation of B-C-N element affects the crystal phase of the catalyst and promotes the generation of heterophase surface heterojunction between (101) and (211). It has certain guiding value for co-doping modification of three elements.
In order to enhance the photocatalytic activity of TiO 2 under visible light, Ag nanoparticles were introduced into tridoped B–C–N–TiO 2 (TT) catalyst by photoreduction deposition. Ag/B–C–N–TiO 2 (ATT) catalysts with the functions of reducing band gap and carrier recombination were prepared. At the same time, the effect of the amount of Ag on the photocatalytic performance of ATT catalyst was investigated. Through XRD , XPS , PL and other characterization methods, the (211)/(101)/Ag interface heterojunction mechanism similar to the traditional Z-scheme heterojunction was proposed. The intervention of Ag nanoparticles changed the P–N interface heterojunction between (211)/(101) to the (211)/(101)/Ag Z-scheme interface heterojunction. The results show that ATT catalyst exhibits the highest photocatalytic activity when the molar amount of Ag is 0.005% with the MB degradation rate of the ATT catalyst (0.01707 min −1 ), which is 14.59 times of TiO 2 (0.00117 min −1 ) and 2.02 times of TT (0.00847 min −1 ). In addition, the four cycles efficiencies of ATT for MB degradation were all above 94.00%.This study reveals the possibility of construction of Z-scheme heterojunctions between precious metal nanoparticles and different interfaces of TiO 2 , and provides a reference for the construction of Z-scheme interface heterojunctions.
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