Preparation And Photoelectrochemical Performance Of ?-Fe₂O₃/Bi₂S₃ Composite Photoanode Grown By Seed Layer-assisted Method

Photoelectrochemical(PEC)water splitting can convert solar energy into hydrogen energy(H₂)by using semiconductor materials,which is a practical and feasible way to solve the problems of fossil fuel exhaustion and environmental pollution.Hematite(?-Fe₂O₃)has many advantages such as suitable band gap width(1.9-2.2 e V),low preparation cost and high photochemical stability.It is one of the photoanode semiconductor materials with great development potential.However,some inherent defects severely limit its practical application in photoelectrochemical decomposition of water.The poor intrinsic conductivity of?-Fe₂O₃leads to a too low migration rate of photogenerated carriers in its body,and most of the carriers are consumed in internal charge recombination.In addition,the short hole diffusion length also causes most of the photo-generated holes was unable to diffuse to the surface of the material to participate in the redox reaction,reducing its PEC performance as a photoanode.In recent decades,a large number of studies on?-Fe₂O₃photoanodes have confirmed that the introduction of a narrow band gap semiconductor with matching energy band position into?-Fe₂O₃is an effective way to improve its light absorption efficiency and charge transfer efficiency in PEC water splitting applications.In this paper,a seed layer-assisted growth mechanism was used to successfully fabricate branched Bi₂S₃nanostructures on?-Fe₂O₃nanorod films.Various characterization methods and photoelectrochemical test methods was used to deeply explore the effect of seed layer on the growth of?-Fe₂O₃/Bi₂S₃composites and the influence of different seed layer deposition times on the PEC performance of?-Fe₂O₃/Bi₂S₃photoelectrode.The specific research content is as follows:(1)The?-Fe₂O₃nanorod array was prepared on the fluorine-doped tin oxide(FTO)substrate by the method of hydrothermal post-annealing.The successive ionic layer adsorption and reaction(SILAR)method was used to deposit a seed layer on the surface of the?-Fe₂O₃film,and then the solvothermal reaction was performed to obtain the final?-Fe₂O₃/Bi₂S₃composite heterojunction.Different composite materials were prepared by changing the number of SILAR deposition cycles for comparison.The morphology and structure of the prepared composite materials were characterized,and the results confirmed that the Bi₂S₃seed layer can assist the better assembly of the branched Bi₂S₃nanorods on?-Fe₂O₃array,which is conducive to the construction of a well-contacted heterojunction interface.The results of Ultraviolet-visible absorption spectroscopy shows that the introduction of Bi₂S₃not only greatly improved the optical absorption intensity of?-Fe₂O₃,but also widens the optical absorption range of the composite electrode to the whole visible region.(2)The photoelectrochemical performance of all prepared samples were tested,and the effect of Bi₂S₃seed layer prepared by different SILAR deposition cycles on the PEC performance of?-Fe₂O₃/Bi₂S₃composite photoelectrode was explored.Through the analysis of the test results,it is concluded that the introduction of the Bi₂S₃seed layer significantly enhances the photocurrent density of the?-Fe₂O₃/Bi₂S₃composite photoanode.Test results of electrochemical impedance spectroscopy(EIS)and Mott Schottky(M-S)show that the coupling of an appropriate amount of Bi₂S₃and?-Fe₂O₃can form a band-matched heterojunction structure,which improves the photoelectrode separation and transmission efficiency of photogenerated carriers,and enhanced performance of photoelectrode PEC.