The Preparation And Photoelectrocatalysis Property Research Of Modified Hematite

The combustion products of hydrogen is only water,and the water splitting can produce hydrogen and oxygen,so hydrogen is considered new energy as it no carbon emission in the future world.Photoelectrochemical cell can make oxygen evolution reaction and hydrogen evolution reaction in anode and cathode respectively,the process convert sunlight into stored energy conveniently in the form of hydrogen,the stable and low-cost photoanode catalyst is crucial in this device.Hematite is considered as one of the most promising photoanode catalysts due to its suitable band gap,high solar to hydrogen efficiency in theory,chemical stability under illumination and abundance in earth.However,the poor conductivity,short photo-generated charge carrier lifetime and high turn-on voltage have limited the performance improvement of hematite severely.The current literatures introduce various nanostructure by different synthesis technologies,enhancement conductivity by elements doping,decrease oxygen evolution overpotential or trap concentration by surface treatment,increase photo-induced voltage or specific area by coupling with other materials.This thesis research is base on solvent thermal synthesis method,then loading co-catalyst on hematite and controlling nanostructure of hematite nanorod array.The nanostructure,composition,physical properties of hematite are characterized by Raman,SEM,TEM,UV,XPS;and its photoelectrocatalysis process are analyzed by LSV,CP,EIS,M-S.Particular content are divided into the following three parts:1.The co-catalyst NiFeB is loaded on naked hematite by moderate chemical reaction.The relative between physical chemical properties and structure of hematite are also researched.Several decade nanoparticles of Ni FeB distribute hematite nanorod surface,sometimes can embed the gap among nanorods.The loaded result can reduce surface capacitance and resistance,decrease open voltage significantly,increase the oxygen evolution reaction dynamics at interface,so the loaded photocurrent density of hematite is improved 170% than unloaded hematite.2.The co-catalyst NiFeP is loaded on bare hematite though quantitative reagents chemical reaction under 250℃.The various loaded mass are also investigated on hematite.There are few tens of NiFeP nanoparticles distribute hematite surface,but the morphology of NiFeP is presented in the form of mesh among hematite nanobars.This loaded structure increase porosity of hematite film and link nanorods each other,the final effect can accelerate charge separation and transfer.The loaded hematite has super photoelectric response stability and photocurrent density is improved 1.5 fold than bare hematite.3.Low molecular polymer is added in aqueous solution when hematite’s precursor β-FeOOH is made,then the polymer produce gas in nanorod under high temperature,this process get coarse porous nanorods.The changed structure increase contact area and charge transfer rate at interface between photoanode and electrolyte.