Iron Oxide Base Film Build And Photoelectrochemical Decomposition Water Performance Research

In the process of photoelectrically driven water splitting,the oxidation semireaction occurring on the photocathode is more difficult in thermodynamics than the half reaction on the cathode that is one of the key factors restricting the efficiency of photoelectrochemical water splitting.Therefore,exploring advanced photoanodes prove still an important topic in the field of water splitting.Among many photoanode materials,α-Fe₂O₃ has received much attention.Because it has the characteristics of rich resources and high chemical stability.what’s more,α-Fe₂O₃ has a moderate band gap width,can respond to visible light in the solar spectrum,and its valence band position is positive compared to the oxidation potential of water which can oxidize water molecules.theoreticallyα-Fe₂O₃ has an optical hydrogen conversion efficiency of up to 15.5%,making it an ideal semiconductor photoanode material.Howeverα-Fe₂O₃ still faces many challenges in the process of photocatalytic splitting of water,includingα-Fe₂O₃ has low electrical conductivity,serious photogenerated carrier recombination,and slow oxygen evolution reaction kinetics during water oxidation.Many studies are exploring corresponding solutions.For instance,element doping,interface modification,conductive substrate nanocrystallization and supported cocatalysts.Based on the above analysis,this article adopts the method of element doping combined with interface modification and supported cocatalyst to modifyα-Fe₂O₃ photoanode,improving its photoelectrochemical water splitting performance.（1）Tin-dopedα-Fe₂O₃,namely Sn-Fe₂O₃,nanostructured films are grown on fluorine-doped tin oxide substrates（FTO）by hydrothermal method,and then FeOOH cocatalyst is loaded on their surface by chemical bath deposition.The introduction of Sn ions to replace part of Fe ions and the oxygen vacancies generated by vacuum heat treatment resulted in the increase defects in theα-Fe₂O₃ lattice,which can improve light absorption.Loading FeOOH on the surface of the Sn-Fe₂O₃ film constructs the“α-Fe₂O₃/FeOOH”heterostructure,which not only enhances the charge separation,but also improves the oxygen evolution kinetics at the electrode/electrolyte interface.When Sn-Fe₂O₃@FeOOH used as the photoanode that show higher photoelectrochemical water splitting performance than pristineα-Fe₂O₃ films.For example,at a potential of 1.6 V（vs.RHE）and AM 1.5G simulated solar irradiation,the photocurrent densities ofα-Fe₂O₃ and Sn-Fe₂O₃@FeOOH for photoelectrochemical water splitting are 0.29 mA×cm^-2and 0.86 mA×cm^-2,respectively,and the latter is nearly two times higher than the former.As a prototype anode in a photoelectrochemical cell these nanostructured Sn-Fe₂O₃@FeOOH films bodes well for their use as a platform for the design and implementation of improved performance photocatalysts for making solar fuels from water.（2）Growth of niobium dopedα-Fe₂O₃ nanostructured films on FTO by hydrothermal method that namely Nb-α-Fe₂O₃,then CoPi cocatalyst was further loaded on its surface by electrochemical deposition.The effect of Nb doping and CoPi cocatalyst modification on the performance of photoelectrochemical water oxidation ofα-Fe₂O₃ is studied in detail.It shows that Nb doping and CoPi modification towardα-Fe₂O₃ not only enhances its light absorption,but also improves its conductivity properties,bulk charge separation efficiency and charge transfer efficiency and accelerates the kinetics of interfacial oxygen evolution reaction.When Nb-α-Fe₂O₃@CoPi is used as photoanode to water splitting,at the potential of 1.6 V（vs.RHE）,its photocurrent density reaches 1.44 mA·cm^-2,which compared to pristineα-Fe₂O₃,it has increased by more than three times and also shows a negative shift of 540 mV in the onset potential.（3）The Si-Fe₂O₃@Fe₂O₃ film has excellent photoelectrochemical performance is prepared by a simple hydrothermal method.Firstly,construct Si⁴⁺dopedα-Fe₂O₃nanostructured thin film（Si-Fe₂O₃）on FTO substrate,then further loadedα-Fe₂O₃ passivation layer in secondary hydrothermal solution.The results show that Si doping and the surface passivation treatment ofα-Fe₂O₃ not only improves the light absorption of purityα-Fe₂O₃,and reduces its charge transfer and transmission resistance.In addition,passivation treatment of surface states is more conducive to the separation of photo generated charge carriers,significantly accelerating their charge transfer process.As expected,the photoelectricchemical water splitting performance of theα-Fe₂O₃ film was significantly improved.At 1.6 V（vs.RHE）potential,the photocurrent density of the Si-Fe₂O₃@Fe₂O₃photoanode can reach 0.95 mA×cm^-2 which is compared to pristineα-Fe₂O₃ has increased by nearly twice.In addation,the onset potential of Si-Fe₂O₃@Fe₂O₃ photoanode when used to photoelectricchemical water splitting was shifted by 140 mV.These results provide a simple and effective strategy for the design of photoanode structures and interface engineering in high-performance photoelectricchemical applications.