The Study On Preparation And Properties Of Fe₂O₃ Base Optical Electrochemical Decomposing Water Photoanode

With the rapid development of the global economy,people are increasingly demanding energy choices,and environmentally friendly new energy sources have received extensive attention.Photoelectrochemical catalytic decomposition of water to produce hydrogen has received widespread attention.Among many photoanode materials for photoelectrochemical decomposition of water,hematite（α-Fe₂O₃）has a narrow band gap,and its theoretical absorption efficiency of solar energy reaches 16.8%at 2.1-2.2 e V.In addition,it has the advantages of non-toxic,harmless,low price,abundant reserves and very stable,making it one of the ideal semiconductor photocatalysts.However,α-Fe₂O₃ also has shortcomings that limit its photoelectric performance:poor conductivity(10^-2cm²V^-1s^-1),short survival time of photogenerated carriers,and serious electron-hole pair recombination.In order to overcome the inherent shortcomings ofα-Fe₂O₃,people use element doping,morphology control,surface treatment,compound semiconductor and other modification measures to improve its photoelectric performance.This article mainly adopts the easy-to-operate,environmentally friendly electrodeposition method and hydrothermal method to prepareα-Fe₂O₃ photoanode.At the same time,the photoanode is improved by element doping,morphology control and surface treatment and other modification measures.The main conclusions as follows:（1）The Fe film was prepared by the cathode electrodeposition method,and then annealed to prepare the originalα-Fe₂O₃ photoanode.The Fe₂O₃-H₂C₂O₄ photoanode was obtained by oxalic acid corrosion,and the modified Fe₂O₃-H₂C₂O₄+TBT photoanode was prepared by oxalic acid corrosion and tetrabutyl titanate soaking.Under the condition of 1.23 V（vs.RHE）,compared with 0.27 m A cm^-2 ofα-Fe₂O₃,the photocurrent density of Fe₂O₃-H₂C₂O₄ photoanode increased to 0.34 m A cm^-2.At the same time,the photocurrent density of the sample Fe₂O₃-H₂C₂O₄+TBT prepared by the cooperative reaction of H₂C₂O₄ and Ti（OBu）₄ increased to 0.59 m A cm^-2.The main reason for the improvement of PEC performance of Fe₂O₃-H₂C₂O₄photoanode is the increase of its specific surface area and carrier concentration.In addition,the PEC performance improvement of Fe₂O₃-H₂C₂O₄+TBT photoanode is not only due to the increase in specific surface area,but also due to the incorporation of Ti,thereby increasing the conductivity.（2）A dendritic F/Ag-Fe₂O₃ photoanode with core-shell structure was prepared by multiple electrodeposition methods.A dendritic Ag film was deposited on the FTO by electrodeposition,and then an Ag-Fe film was obtained by electrodeposition again,so that its morphology was controlled.Under 1.23V（vs.RHE）bias,the photocurrent densities ofα-Fe₂O₃ and F/Ag-Fe₂O₃ photoanodes are 0.14m A cm^-2 and 0.77 m A cm^-2,respectively,the photocurrent density of F/Ag-Fe₂O₃ photoanode is 5.5 times that ofα-Fe₂O₃ photoanode.The main reason for the improvement of the photoelectric performance of F/Ag-Fe₂O₃ photoanode is the improvement of conductivity and the increase of specific surface area,which leads to a significant improvement in its bulk charge separation efficiency and surface charge injection efficiency.（3）Theα-Fe₂O₃ photoanode doped withⅣB group ions was prepared by in-situ hydrothermal method.It was found that the photoelectrochemical performance of the doped atom ratio was 1.5at.%to achieve the best,and with the increase of the doping element radius,The photoelectric performance of Fe₂O₃ photoanode is improved more significantly.Under 1.23V（vs.RHE）,the photocurrent density increased from 0.43 m A cm^-2 of basic iron oxide to0.64 m A cm^-2,0.94 m A cm^-2 of Ti-Fe₂O₃,Zr-Fe₂O₃,and respectively,photocurrent density of Hf-Fe₂O₃increased to 1.04 m A cm^-2.The main reason for the enhanced photoelectric performance of the IVB ion dopedα-Fe₂O₃photoanode is that the doped ions cause the increase of the donor concentration,which enhances its conductivity,and at the same time increases the crystallinity of the sample and makes its active surface area larger.As the radius of group IVB ions increases,the number of protons in the nucleus of the ion increases,and the attraction to electrons outside the nucleus is greater,the electron concentration is higher,and the photoelectric performance is stronger.