Study And Application Of Metal Oxide Photoanode And Its Photoelectric Properties

The energy crisis and environmental pollution are severely limiting economic development.The implementation of"carbon peaking"and"carbon neutrality"has led to the development of global energy and industry towards a greener and more sustainable direction.However,our energy sources are still mainly based on fossil fuels.Therefore,the development of alternative,renewable energy sources is an urgent necessity.Photocatalysis（PEC）has long been of great interest for water decomposition and the detection of environmental pollutants.Among them,excellent multifunctional photoelectrode materials play a crucial role in the catalytic performance of PEC.However,the common single photoactive materials are limited in PEC water splitting and PEC sensing applications due to various defects,such as narrow light absorption range,severe photocorrosion,the slow separation rate of photogenerated carriers,and fast compounding rate.Therefore,researchers have devoted themselves to modifying single materials to make them more catalytically active by using different strategies,such as doping,construction of heterojunctions,surface sensitization,and loading of co-catalysts,which are common.In this thesis,we investigated the application of commonly used semiconductor materials TiO₂ and Bi VO₄ in PEC water splitting and PEC sensing.To improve the problems of fast photogenerated carrier complexation rate and slow charge separation rate in single TiO₂ and Bi VO₄ materials,we used different strategies to modify the single materials to some extent.Specifically,the TiO₂ photoanodes were modified both ontologically and on the surface,and the interfacial charge transfer process and surface photoelectrochemical kinetic behavior in the TiO₂ semiconductor photoanode system were investigated under the synergistic effect of both.In addition,this paper also investigates the assembly of Bi VO₄ with the semiconductor photoactive material In₂S₃ to form type II heterojunction photoanodes to improve the PEC hydrolysis performance and the loading of layered hydroxide（FeOOH）on the surface of Bi VO₄ to build a PEC sensing platform for the detection of hexavalent chromium,as follows:1.Double-modified TiO₂ photoanode to enhance PEC water splitting efficiencyNanostructured titanium dioxide（TiO₂）based PEC hydrolysis can be a promising strategy for low-cost production of H₂ to replace fossil fuels and achieve a carbon-neutral society.In this paper,in situ in doping of TiO₂ crystal structure,i.e.,Sn-TiO₂,was achieved by a simple hydrothermal method.it was found that tin doping could significantly increase the carrier density and electrical conductivity of TiO₂.In addition,Ni Co₂O₄ was grown on Sn-TiO₂ nanorods by electrodeposition as a co-catalyst to obtain optimized Ni Co₂O₄/Sn-TiO₂ dual-modified photoanodes.The integrated dual-modified photoanode Ni Co₂O₄/Sn-TiO₂ can reach a photocurrent density of 1.29 m A·cm^-2 at 1.23V（V vs RHE）,which is 2.63 times that of pristine TiO₂,and the photoanode has good stability.This work shows that the PEC performance of TiO₂ photoanodes can be improved by promoting charge separation and slowing down carrier complexation with the synergistic effect of both native and surface modifications.The experimental design of this paper can provide new insights into the rational design and construction of efficient TiO₂ photoanode PEC decomposing water devices.2.Construction of In₂S₃/Bi VO₄ composite photoanode and study of its photoelectric propertiesWe have successfully constructed In₂S₃/Bi VO₄ type II heterojunction photoanodes by hydrothermal growth of In₂S₃ on the surface of Bi VO₄ photoanodes and found that the electron transfer from the conduction band of In₂S₃ to the conduction band of Bi VO₄,the successful construction of the heterojunction improved the charge separation and transfer rate of the system,and significantly enhanced the PEC hydrolysis performance of the photoanodes.Besides,the growth of In₂S₃ broadens the visible light absorption range of the photoanode.The photocurrent density of the integrated photoanode In₂S₃/Bi VO₄ at1.23 V（V vs RHE）is 2.93 times higher than that of the single Bi VO₄ compared to the bare Bi VO₄.We also further characterized the charge transport properties in the integrated heterojunction photoanode by intensity modulated photocurrent spectroscopy（IMPS）and scanning photoelectrochemical microscopy（SPECM）techniques,and the results showed that the formation of heterojunction promoted the hole transport.3.FeOOH/Bi VO₄ photoanode for photoelectrochemical detection of hexavalent chromiumThe construction of a highly sensitive photoelectrochemical（PEC）sensing platform is of great application for the detection of trace pollutants in the environment.We have integrated FeOOH/Bi VO₄ photoelectric sensors by using a combination of electrodeposition and hydrothermal methods to decorate layered hydroxide FeOOH on the surface of nanoporous Bi VO₄ photoanodes as a co-catalyst to achieve sensitive detection of Cr（VI）.The loaded FeOOH co-catalyst retarded the charge recombination of the Bi VO₄ photoanode and promoted the charge transfer of the system,thus obtaining an amplified and stable photocurrent signal for the detection of hexavalent chromium.In the PEC sensing system,Cr（VI）as a reducing agent is reduced to Cr（Ш）by consuming the electrons gathered on the conduction band of the Bi VO₄ photoanode,which inhibits the electron transfer and leads to the attenuation of the PEC signal.The developed FeOOH/Bi VO₄ PEC sensor for the detection of Cr（VI）has a high sensitivity in the range of 1-400μM with a detection limit of 0.043μM.