The Preparation And Study Of α-Fe₂O₃Photoanode And PbTiO₃Photocathode Doped And Grafted By Fe（Ⅲ） Ions For Water Splitting

Photocatalytic hydrogen generation by water splitting from semiconductors has beenconsidered as one of the best ways to convert a naturally abundant substance into anenergy source. For water splitting, photoelecrodes should have the following advantages:high photoelectric conversion efficiency, good visible light response, cheap, stability andso on. In this paper, the preparation and photoelectrochemical (PEC) properties of α-Fe2O3thin film photoanode etched by HF and PbTiO3photocathode doped and grafted by Fe (III)ions have been researched.(1) The effects of HF treatment on the PEC properties of sol-gel prepared hematite(α-Fe2O3) thin films were investigated. Pores and the interstices between the grainsdeveloped on the film surface as the HF etching time increased. The photocurrent of theα-Fe2O3photoanode decreased firstly within5minutes of etching, and then increasedquickly as the etching time added. Longer time than15minutes deteriorated thephotocurrent again, while re-annealing the etched samples enhanced the photocurrentgreatly. Based on the analysis of electrochemical impedance spectroscopy, Raman andx-ray photoelectron spectra, it was proposed that, two factors, the porosity and loweredcrystallinity of the α-Fe2O3surface due to the HF treatment, contributed to the photocurrentreversely. A schematic model was then drawn to explain the enhanced PEC activities ofthe etched plus re-annealed α-Fe2O3photoanode. The PEC and water splittingmeasurements showed that the etched plus re-annealed photoanode is more stablecomparing with the as-prepared one, and a Faradic efficiency is up to90%during water splitting.(2) The PEC activity of the PbTiO3film photocathode deposited on ITO-coated quartzsubstrates was significantly improved through modifying the film surface by both the Fe(III) doping and grafting. Doping the PbTiO3with Fe (III) ions narrows its band gap whichincreases the visible light utilization, while the surface-grafted Fe (III) ions on the dopedPbTiO3surface help improving the charge transfer on the photocathode/electrolyteinterface. By such way, the photocurrent was increased from38A/cm2to210A/cm2under100mW/cm2Xe lamp and0.1M Na2SO4as electrolyte and zero-bias versus SCE.