Preparation Of BiVO₄-based Nanostructured Composite Films By Electrospray Technique For Photoelectrochemical Water Splitting

With the global energy shortage and environmental pollution becoming more and more serious,it is very important to develop clean and renewable energy.Solar energy is rich,green and sustainable,which is expected to solve these challenges.However,the intermittence and fluctuation of solar energy make it difficult to replace fossil fuel for practical production.Photoelectrochemical?PEC?water splitting can convert solar energy into hydrogen energy,which has a good application potential in solar energy utilization.As a key component of PEC system,researchers have been trying to develop stable,efficient and cheap electrode materials to achieve more than 10%of the solar-hydrogen energy conversion?STH?efficiency.Because charge separation and transport play a decisive role in the performance of electrode materials,Researchers have developed a variety of strategies to improve charge separation and transport efficiency,such as the construction of nanostructures with high specific surface area,the introduction of dopants,the regulation of active crystal surface,the design of junctions and the modification of interfaces,or a combination of multiple strategies.Among them,the design of heterojunction has attracted special attention because it can combine two or more semiconductors with complementary photosensitive properties.In addition,the synthesis method also has an important influence on the properties and morphology of the electrode materials.In this paper,BiVO₄/FeVO₄and WO₃/BiVO₄ heterojunction thin films were prepared by electrospray deposition technology.The effects of substrate temperature and the amount of deposition on the properties of the films were investigated.The thickness ratio of the composite films was adjusted by changing the ratio of precursor solution.The reasons for the improvement of the properties were explored by analyzing the characterization results of the materials:1?We have coupled BiVO₄ with narrow band gap semiconductor FeVO₄ and successfully fabricated BiVO₄/FeVO₄ composite thin films on FTO substrates by electrospray technology.The size of BiVO₄ nanoparticles prepared by this method is about 200-300 nm,which is like"worm",with good porosity,which can effectively shorten the transmission distance of photogenerated carriers.FeVO₄ nanoparticles?100-200 nm?can be uniformly deposited on the surface of BiVO₄ film.When the film thickness ratio is 1:1,the photocurrent density of the composite film reaches 0.4mA cm^-22 at 1.23 V_RHE,which is 6 times higher than that of the single-phase BiVO₄film(0.06 mA cm^-2).Through the analysis of EIS results,the improvement of electrode performance can be attributed to the formation of heterostructure at the two-phase interface,which promotes the effective separation of carriers.2?We have coupled BiVO₄ with wide band gap semiconductor WO₃ and fabricated WO₃/BiVO₄ composite thin films on FTO substrates by electrospray technology.The size of WO₃ nanoparticles prepared by this method is about 100 nm,which is"strip"due to the influence of solvent.BiVO₄ nanoparticles were deposited on the surface of WO₃ film.WO₃ and BiVO₄ have complementary photosensitive properties and good band matching.When the film thickness ratio is 2:1,the maximum photocurrent density of the composite film is 1.59 mA cm^-2,which can maintain good stability in a certain period of time.Through the comparative analysis of the characterization results of the materials,we can attribute the significant improvement of the electrode performance to the appropriate band arrangement,which realizes the effective charge transfer,and the existence of BiVO₄ layer,which widens the optical response range.In this paper,BiVO₄/FeVO₄,WO₃/BiVO₄ composite films were prepared by electrospray deposition technology.It provides an environmentally friendly and low-cost process for the preparation of electrode materials.It also provides a new idea for the synthesis of spinel and perovskite materials in lithium ion batteries,gas sensitive and supercapacitors.