Study On Preparation,Modification And Photoelectrochemical Properties Of Fe₂O₃ Nano Arrays

Photoelectrochemical(PEC)water splitting,an approach to harvest solar energy to produce clean hydrogen fuel by semiconductor electrodes,offers an effective solution to energy crisis and environment pollution.Among all the available semiconductor materials,hematite(?-Fe2O3)has emerged as an attractive candidate for PEC photoanode materials due to its favorable optical band gap(2.0-2.2 eV),excellent chemical stability,natural abundance,low cost and nontoxicity.It has been theoretically predicted that ?-Fe2O3 can achieve a solar-to-hydrogen efficiency of 16.8%.However,the performance of ?-Fe2O3 is considerably lower than theoretical predictions.The main factor limiting its efficiency is severe carrier recombination of ?-Fe2O3 restricted by its low electron mobility,short diffusion length of holes(2-4 nm)and poor oxygen evolution reaction(OER)kinetics.In this regard,this study was performed to improve separation efficiency of photogenerated electron-hole pairs and enhanced PEC properties of ?-Fe2O3 by doping,constructing heterostructure and sensitized with quantum dot.The research contents are as follows:(1)Ti-Fe2O3/CdS heterojunction arrays with Ti-Fe2O3 nanosheet cores and CdS shells were fabricated and demonstrated its application as a photoanode for PEC water splitting.Ti doping into the hematite promotes the conductivity and simultaneously extends the spectral responsive range of hematite.CdS here builds heterojunction with Ti-Fe2O3 to improve the separation and transportation of the photo induced electrons and holes.By virtue of these combined effects,Ti-Fe2O3/CdS heterojunction showed a cathodic shift of the onset potential and a notable improvement of the photocurrent density.(2)Investigating the effect of CQDs as sensitizer on the PEC properties of Fe2O3 photoanode.UV-vis results showed that CQDs/Fe2O3 film exhibits much higher absorption both in visible light and near-infrared light.EIS results revealed the role of the CQDs in reducing the charge transfer resistance at the electrode/electrolyte interface.The photoelectrochemical study showed that the photocurrent density of CQDs/Fe2O3 film at 0.23 V bias potential is about 25 times of that of the bare Fe2O3 electrode.