The Study On The Construction And Photocatalytic Performance Of Co/Ni Metal （Complex,MOF）/BiVO₄ Composite

Due to the current energy crisis and environmental pollution,the demand of human beings to explore sustainable and clean energy to replace fossil fuels has become increasingly huge.In recent years,the research on the decomposition of hydrogen in aquatic products by solar energy driven photoelectrochemistry（PEC）has been regarded as one of the ways of environmental protection,which has become the research focus to solve these two problems.Among many semiconductors,BiVO₄ has become a leader in this field due to its proper band gap（².4 eV）,enough positive valence band edge（VB,².4 eV）,its large presence on the earth and excellent PEC stability.There are still some disadvantages of BiVO₄ photoanode in water decomposition of PEC,such as low electron mobility,serious electron hole recombination and slow surface water oxidation.In order to achieve effective water decomposition of PEC,it is very important to overcome the recombination of electron hole on the surface of BiVO₄ photoanode.Therefore,the research and development of efficient and stable photocatalyst has become a research hotspot in the field of photocatalysis.In this paper,BiVO₄ based composite photo electric materials were prepared by hydrothermal method and solvothermal method,and their photocatalytic properties were studied.The structure and morphology of the composite were characterized by Scanning electron microscopy（SEM）,Transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,Ultraviolet visible diffuse reflectance（Uv-Vis DRS）,Fourier transform infrared spectroscopy（IR）,photocurrent performance test,etc.The specific research contents are as follows:（1）Firstly,BiVO₄@Co-MIm composite electrode material was synthesized by a simple water bath method with cobalt nitrate pentahydrate as cobalt source and 2-methylimidazole as structure directing agent.The composite electrode was used in the condition of AM 1.5G light source,0.5 M Na₂SO₄ electrolyte and 1.23 Vvs.RHE bias voltage.The results show that the properties of the composite photoanode prepared by different water bath time are higher than that of the pure BiVO₄ electrode,and the BiVO₄@Co-MIm composite electrode with water bath time of two hours has the best photoelectric properties.Based on the analysis of the experimental results,the most possible photocatalysis mechanism of the composite electrode materials was proposed.（2）The 3D CoNi-MOFs/BiVO₄ composite photoelectrode material was synthesized by a simple solvothermal method with BiVO₄ as the substrate material,and its photocatalytic performance and stability were tested.The results show that under the light source of AM 1.5G,the composite photoanode material,CoNi-MOFs/BiVO₄,has better photocatalytic performance than pure BiVO₄,and the highest photocatalytic performance is shown when the molar ratio of Co to Ni is 1:1.At the bias voltage of 1.23 Vvs.RHE,the photocurrent density can be as high as 3.3 mA/cm².（3）2D Ni-MOF/BiVO₄ composite photoanode materials were prepared by hydrothermal method,and the composite samples were applied to the experiment of the PEC water splitting.The experimental results show that under AM 1.5G,the photoelectric performance of the composite electrode is nearly twice that of pure BiVO₄ photoelectrode.Because the 2D Ni-MOF nanomaterial not only has a nano-scale thickness,which accelerates the separation of electron-hole pairs in the composite,but also has a high proportion of active sites,which improves the photocatalytic activity of the composite and accelerates the water oxidation reaction.