Synthesis And Photocatalytic Activity Of Bi Self-Doped BiVO₄ Catalyst

Photocatalytic technology is considered as one of the most potential technologies to solve energy and environmental problems,and the key is to develop photocatalytic materials.Monoclinic bismuth vanadate?BiVO₄?with a band gap energy about 2.4eV,is a promising visible light-driven catalyst for water splitting and oxidative decomposition of organic pollutants.Since the photocatalytic efficiency of bismuth vanadate is not ideal due to the low separation efficiency of electron-hole pairs,improving the photocatalytic efficiency of bismuth vanadate by modification is the key to expand its applications.Metal element self-doping can improve the photocatalytic performance of photocatalyst and avoid the negative effects of extraneous element doping.In this paper,bismuth vanadate was prepared by using bismuth chloride and hydrated bismuth nitrate as bismuth source,respectively.The enhanced photocatalytic activity of bismuth vanadate by Bi self-doping was investigated.1.A series of Bi self-doping bismuth vanadate with different doping contents were synthesized by adjusting the stoichiometric ratio of BiCl₃ and Na₃VO₄ using solvothermal method.The UV-vis DRS spectra showed that Bi_xVO₄ with different Bi contents had similar absorption edges,and Bi doping could effectively improve the absorption intensity of visible light.The results of photocurrent and EIS measurements showed that Bi doping could decrease impedance of bismuth vanadate and enhance the separation and conduction efficiency of photogenerated electron-hole pairs.The results of photocatalytic degradation experiments showed that 0.2 g/L Bi_1.0VO₄ degraded 72% methylene blue?MB?and 79% rhodamine B?RhB? with a concentration of 20 mg/L under 500 W Xenon lamp irradiation for 3h,while the corresponding degradation rates of MB and RhB over 0.2 g/L Bi_1.3VO₄ with the best photocatalytic activity reached 83% and 88%,respectively.2.A series of bismuth vanadate with different Bi doping contents were synthesized by using Bi?NO₃?₃·5H₂O instead of BiCl₃ as bismuth source under the same conditions.The SEM and TEM images showed that the morphologies of the samples were irregular lamellar structure,which was different from the smooth lamellar structure of Bi_1.3VO₄ prepared by BiCl₃ as bismuth source,and the thicknesses and particle sizes of the samples were increased.The results of photocatalytic degradation experiments showed that the degradation rates of MB and RhB with the same concentrations of 20 mg/L over0.2 g/L N-Bi_1.0VO₄ were 68% and 75% under 500 W Xenon lamp irradiationfor 3 h,respectively,while the degradation rates of MB and RhB for N-Bi_1.2VO₄ catalyst with the best photocatalytic activity reached 74% and 81%,respectively.The photocatalytic activity of Bi self-doped bismuth vanadate was improved,but the degradation efficiency of the samples was lower than that of the corresponding catalysts prepared using BiCl₃ as bismuth source.3.On the basis of the successful synthesis of Bi self-doped bismuth vanadate,Bi_1.3VO₄ with the best photocatalytic activity was selected to be combined with CuO to improve its photocatalytic performance in further.The images of SEM and TEM revealed that CuO/Bi_1.3VO₄ were also lamellar,compared with Bi_1.3VO₄,however,the size and thickness of the samples were increased.The results of BET analysis showed that the specific surface areas of the composite samples increased significantly.The UV-vis-DRS spectra showed that the incorporation of CuO had a great effect on the band gap structure and absorption edge of bismuth vanadate catalyst,which could decrease the band gap of bismuth vanadate and make the absorption edge shift to long wavelength obviously.The photocurrent and EIS measurements showed that the separation and conduction efficiency of photogenerated electron-hole pairs of bismuth vanadate samples increased by incorporation with CuO.The results of the photocatalytic degradation experiments showed that the degradation rates of MB and RhB with the same concentrations of 20 mg/L over 0.2 g/L 1CuO/Bi_1.3VO₄ with the best photocatalytic activity were 80% and 90% under 500 W Xenon lamp irradiation for 2 h,while the corresponding degradation rates of MB and RhB for Bi_1.3VO₄ catalyst were only 72% and 82%,respectively.