Synthesis And Properties Of Bismuth Vanadate Photocatalytic Composite Materials Performance Study

Due to the continuous advancement of science and technology and the rapid expansion of the population,environmental problems have gradually become the biggest challenge that people face now.Degradation of pollutants by semiconductor photocatalyst is an environmentally friendly technology,and TiO₂ as a photocatalyst has been widely concerned.However,TiO₂ has a large band gap（3.2ev）,which results in its inability to degrade in visible light.In order to make better use of solar energy,many photocatalysts driven by visible light have been developed.Bismuth vanadate has attracted people’s attention due to its suitable band gap（2.4eV）,good visible light response ability and non-toxic and harmless characteristics.In this paper,bismuth vanadate was used as the substrate of photocatalyst to improve the photocatalytic degradation performance.Through a series of tests and characterization,the successful synthesis of the composite photocatalyst was proved and the reasons for the performance improvement were analyzed.Finally,the possible mechanism was proposed.The main content consists of the following three parts:（1）A simple hydrothermal method was used to obtain Co-Ni（OH）₂ and BiVO₄,then the two powders were mechanically mixed,and CoNiO_x/BiVO₄ was obtained by heat treatment at 320℃in muff furnace.Compared with pure BiVO₄,the photocatalytic degradation performance of the composite photocatalyst was improved by 44.3 times.The morphology and lattice structure of the samples were studied by XRD,TEM and XPS.In order to further explore its photocatalytic mechanism,we conducted a series of experiments including DRS,PL,ESR and EIS to verify our conjecture.The results showed that the close connection between CoNiO_x and BiVO₄ significantly increased its photocatalytic activity.（2）The metal palladium and silver were deposited on the surface of bismuth vanadate by chemical reduction.The atomic ratio was first screened to find the best rescreened mass ratio.The group of catalysts with the best performance could degrade85%of the organic dye in 80min.By means of XRD,TEM,XPS and other characterization methods,the noble metal was successfully loaded.At the same time,a possible photocatalytic mechanism was proposed according to the results of various electrochemical tests and ESR experiments,and the main active groups were obtained by trapping agent experiments,which proved the proposed mechanism.（3）The surface of bismuth vanadate was etched with hydrochloric acid solutions of different concentrations,and then BiOCl was loaded onto the surface of BiVO₄ by hydrothermal method,and Au was loaded onto the surface of the composite catalyst by means of chemical reduction.BiVO₄,BiOCl/BiVO₄ and Au/BiVO₄ showed better activity and stability.The structure and morphology of the composite photocatalyst were studied by means of XRD,TEM and XPS.The active groups involved in the catalytic process were tested by ESR and the possible photocatalytic mechanism was proposed.