Rational Construction Of ?-Fe₂O₃ Based Photoanode And Its Study On Photoelectrochemical Water Oxidation

Photoelectrochemical water splitting is an effective means of alleviating energy crises and environment pollution.However,the energy conversion efficiency of this technology is still very low,which is difficult to meet the requirements of industrialization.The main reasons are the intrinsic limitations of the photoanode including:the sluggish oxygen evolution kinetics,poor stability,lower light absorption efficiency,carrier separation efficiency and injection efficiency.This challenge is probably best exempliled by hematite??-Fe₂O₃?,Therefore,to solve the above problems and obtain a highly active and stable photoanode material is the main purpose of this paper.And the above problems were solved by heteroatom doping,p-n junction/homojunction structure construction,co-catalyst support in this paper.The content of this paper mainly includes the following three parts.1:NiO Nanoparticles Anchored on Phosphorus-Doped a-Fe₂O₃ Nanoarrays:An Efficient Hole Extraction p–n Heterojunction Photoanode for Water OxidationIn this work,a photoanode consisting of NiO nanoparticles anchored on a gradient P-doped?-Fe₂O₃ nanorod?NR?array?NiO/P-?-Fe₂O₃?was fabricated to achieve optimal light absorption and charge separation,and rapid surface reaction kinetic.Specifically,the photoanode with the NR arrays structure allowed high mass transport rate to be achieved while the P-doping effectively decreased surface trapping sites and improved the electrical conductivity of?-Fe₂O₃.Furthermore,the p-n junction formed between the NiO and P-?-Fe₂O₃ can further improve the PEC performance due to the efficient hole extraction property and water oxidization catalytic activity of NiO.Consequently,the NiO/P-?-Fe₂O₃ NR photoanode produced a high photocurrent density of 2.08 mA cm^-2 at 1.23V vs.RHE and a 110 mV cathodic shift of the onset potential.2:Facile regrowth of Mg-Fe₂O₃/P-Fe₂O₃ homojunction photoelectrode for efficient solar water oxidationWe developed a regrowth strategy to fabricate a photoanode with metallic Mg-doped?-Fe₂O₃coating on nonmetallic P-doped?-Fe₂O₃ nanorods?Mg-Fe₂O₃/P-Fe₂O₃ NRs?.This homojunction structure fulfils the requirements of both high charge separation efficiency and favorable band alignment,showing a high photocurrent density?4.7-fold higher than pristine Fe₂O₃?and low onset potential of 0.68 V_RHE.Experimental and density functional theory?DFT?results reveal that the origin of such superior PEC performance is P-doping and Mg-Fe₂O₃ coating,which efficiently eliminate lattice mismatching,improve the conductivity of hematite,and simultaneously promote the photogenic carriers separation by the built-in electric field.3:Construction of efficient hole migration pathway on hematite for efficient photoelectrochemical water oxidationIn this work,we construct an efficient hole migration pathway by integrating the co-catalyst?NiOOH?onto the homojunction structured?-Fe₂O₃ coating on F doped?-Fe₂O₃ nanorods?NiOOH/Fe₂O₃/F-Fe₂O₃ NRs?,which exhibits a higher photocurrent density?3.4-fold higher than pristine?-Fe₂O₃?and lower onset potential of 0.61 V_RHE than most reported hematite-based photoanodes.Detailed physical characterization and electrochemical experiments results reveal that the origin of such superior photoelectrochemical water oxidation performance is due to the F-doping,built-in field formation and efficient hole extraction.This new designed photoanode fulfils the requirements of low surface trapping sites,high conductivity,efficient charge separation and injection efficiency.