The Study On The Preparation,Characterization And Photoelectrochemical Performance Of The Porous Hematite Photoanodes

Along with the rapid development of economy,the energy shortage and environmental problems have been worsening,thus,it is very important to develop clean and efficient energy technologies.Since hydrogen exhibits high heating value and water is the product in the process of hydrogen combustion,thus it has been regarded as a clean energy.Photoelectrochemical(PEC)water splitting is an ideal way to produce hydrogen by direct conversion renewable solar energy to hydrogen.During the past four decades,many efforts have been made to develop effective,cheap and stable photoelectrode materials for water splitting.Among the materials,hematite(a-Fe2O3)has been extensively studied as a promising candidate photoanode because of its favorable band gap(2.0-2.2 eV),non-toxicity,low-cost and excellent chemical stability and operation durability.In this work,ion doping and rapid thermal annealing have been adopted to overcome the shortages of bulk a-Fe2O3(e.g.poor the electronic conductivity,small surface area),thus the obtained hematite photoanodes exhibited enhanced PEC performance due to the improved electronic and structural porperties.The detail is as follows:(1)Ti-doped hematite films were grown on transparent conductive fluorine-doped tin oxide(FTO)glass by hydrothermal from the solution of FeCl3 and TiOCl2 in presence of NaF,followed by an appropriate annealing.The hematite films were studied by EDX,SEM,TEM to analyze the composition,morphology,structure and the PEC water splitting performance in detail.On the basis of the obtained results,the enhanced PEC performance could be attributed to the improved structural,electrical and charge transfer properties.(2)By virtue of graphite powder as a susceptor,porous hematite photoanodes with wormlike networks were prepared by microwave-assisted rapid annealing of?-FeOOH grown directly on FTO glass.The obtained characterization results show that,the enhanced electrochemical characteristics such as enlarge surface area and the enhanced wetting property lead to the excellent PEC performance toward the solar-driven water splitting for hydrogen production.The hematite electrode exhibited an enhanced PEC water oxidation activity with IPCE of 51%at 340 nm under the potential of 1.23 V vs.RHE.The novelties and innovations of this study are as follows:(1)Considering the fact that fluoride anion can coordinate with metal ions(Fe3+,Ti4+)and form stable complex to balance the hydrolysis rate between Fe3+ and Ti4+,the uniform doping of Ti in hematite film was achieved;(2)Rapid thermal annealing via microwave can separate the relatively slow processes of particle growth and avoid the collapse of nanostructure from other processes occurring during the annealing process,thus the rapid conversion of inert FeOOH into Fe2O3 with high performance can be achieved through the microwave-assisted annealing.