Performance Of WO₃/BiVO₄ Composite Photoanode For Photocatalytic Water Splitting

The use of solar energy to drive water decomposition to produce hydrogen is an effective means to alleviate the current energy and environmental crisis.Water decomposition includes water oxidation and water reduction.Water oxidation has become the bottleneck of current research.Therefore,people are looking for suitable semiconductor materials to build photoanode for water oxidation.How to improve the efficiency of water oxidation is the current boom.In the early stage,TiO₂ was mainly used,but its forbidden band width was too narrow,and the utilization rate of sunlight was too low.However,TiO₂ semiconductors had obvious defects,and the band gap was wider at about 3.2 ev,which was only applicable to solar energy spectrum.The light response in the ultraviolet region is too low for the utilization of sunlight,the quantum efficiency is low,and the probability of recombination of photogenerated carriers is large.Therefore,in this dissertation,a heterojunction using WO₃ as an electron conductor and BiVO₄ as a light-absorbing layer was designed.The CoO_x was used as a water oxidation catalyst to modify the heterojunction and a composite photoanode was constructed.The phosphate buffer solution?p H = 6.84?was used for electrolysis.Liquid,Ag/Ag Cl as reference electrode,and Pt electrode to form PEC.Under visible light irradiation,the WO₃/BiVO₄ heterojunction produces electron and hole pairs to separate states.The electrons are transported from the conduction band of BiVO₄ to the conduction band of WO₃,and then transported to the counter electrode to complete water reduction to release H2.The hole is derived from WO₃.The valence band transported to BiVO₄ is further transported to the CoO_x catalyst to complete the oxidation of water to release O₂,completing the entire photocatalytic water decomposition process.However,the Pt electrode used in the PEC is used as the electrode to reduce water to release the hydrogen half-reaction,in which the Pt electrode is too costly and requires a large bias to achieve good performance,and essentially uses electric energy.It loses the significance of developing new energy sources.It is a good way to replace the external bias by designing the device,which is also one of the most promising methods for large-scale practical application in the future.Therefore,we chose Ni O and sensitized with Sb₂S₃ to build a Ni O/Sb₂S₃ composite photocathode and a WO₃/BiVO₄ composite photoanode in series to form p/n PEC.The photocatalytic total water decomposition was achieved without external bias.