Preparation Of Fe₂O₃ Based Photoanode Materials And Photoelectrochemistry Properties Reaserach

Photoelectrochemical?PEC?water splitting has attracted more attention due to the production of clean and renewable hydrogen energy to resolve the coming energy crisis.However,the PEC water splitting still faces many challenges,and the biggest of which is to construct an efficient photoanodes with effective charge separation and high surface reactivity.Among various semiconductors,hematite?Fe₂O₃?is one of the most promising photoanode materials due to its abundance,high photochemical-stability,non-toxicity,and suitable bandgap?1.9-2.2 eV?.However,the PEC performance of hematite has been generally restricted by the intrinsically poor conductivity,high charge recombination,and sluggish oxygen evolution reaction?OER?kinetics.Thus,great efforts have been devoted to promoting the PEC performance of hematite,such as element doping,morphology controlling,surface modification and heterojunction construction.In this work,Fe₂O₃ was modified by both doping and surface modification,and the photoanode materials were characterized to determine the reasons for the improvement of the PEC performance,which provided theoretical and experimental evidences for designing and preparing efficient photoanode materials.The main contents of this thesis are as follows:1.Preparation of MnO₂ cocatalyst modified P-doped Fe₂O₃ photoanode and PEC properties reaserach.We used hydrothermal and calcination methods to grow Fe₂O₃ nanorods arrays on the surface of FTO.Phosphorus was doped into the Fe₂O₃ by a simple impregnation method,and then the Mn O₂ cocatalyst was modified on the surface of the P-doped Fe₂O₃ by a facile dipping and annealing method.The results of PEC tests shown that P doping enhanced the carrier density of the photoanode(from 3.44×10¹⁹cm^-3to 9.09×10¹⁹cm^-3),MnO₂cocatalyst promoted the surface charge separation.The photocurrent density of MnO₂/P:Fe₂O₃ reached 1.65 mA·cm^-2at 1.23 V vs.RHE?Reversible Hydrogen Electrode?,which was about four times higher than that of pristine Fe₂O₃(0.35 mA·cm^-2).The carrier density and charge separation efficiency of doped and modified Fe₂O₃ photoanode materials have been greatly improved,and the impedance decreased significantly.2.Preparation of FeO_1-xOH cocatalyst modified P-doped Fe₂O₃ photoanode and PEC properties reaserach.Fe₂O₃ nanorods arrays were grown on the surface of FTO by hydrothermal and calcination methods.Phosphorus doping was introduced into the Fe₂O₃ by dipping,which significantly improved the conductivity;then the FeO_1-x-x OH cocatalyst was deposited on the surface of P-doped Fe₂O₃ by impregnation to enhance the OER kinetics.The photocurrent density of FeO_1-xOH/P:Fe₂O₃ reached 2.10 mA·cm^-2at 1.23 V_RHE,which was more than four times higher than that of pristine Fe₂O₃(0.43 mA·cm^-2).The analysis shows that Fe²⁺plays a major role in the FeO_1-xOH cocatalyst and it can be oxidized by photogenerated holes to Fe³⁺.Fe³⁺can oxidize water quickly and itself reduced to Fe²⁺.Not only enhance the OER kinetics,but also promotes charge separation.