Study On The Modification Of Hematite Photoanode And Its Photoelectric Catalytic Water Splitting Performance

Hydrogen energy is considered to be one of the most promising clean energy sources in the 21st century due to its high energy density,pollution-free and renewable.Hydrogen production using solar photoelectrochemical?PEC?water splitting is a feasible way to obtain hydrogen energy,and this field has received extensive attention from researchers.In this paper,hematite??-Fe₂O₃?photoanode is used as the basis,and its PEC water splitting performance is studied through modification.In this paper,a simple and rapid method for the preparation of?-Fe₂O₃ thin films is designed by electrochemical methods.First,different Fe thin films are prepared under constant potential conditions using Fe Cl₃ electrolyte at different electrodeposition potentials,electrolyte concentrations,and electrodeposition times.Then,the?-Fe₂O₃ photoanode was obtained by rapid annealing at high temperature,and then the Co₃O₄nanoparticles were further composited with the hydrothermal method.Through a series of characterization testing methods,the effects of different preparation conditions and Co₃O₄ nanoparticles on the water oxidation performance of hematite photoanode PEC were studied.The results show that when the electrodeposition potential is-1.2V vs.SCE,the Fe Cl₃ electrolyte concentration is 6m M,and the electrodeposition time is 420s,the?-Fe₂O₃ photoanode PEC prepared under this condition has the best water oxidation performance.After further loading Co₃O₄nanoparticles,the Co₃O₄/?-Fe₂O₃ photoanode can reach 0.77 m A cm^-2 at 1.23V vs.RHE,which is 0.71 times higher than a single hematite,and the starting potential is negative shifted by 150 m V.Through analysis,Co₃O₄ nanoparticles can not only act as co-catalysts,greatly enhance the kinetics of water oxidation of hematite,as a p-type semiconductor,but also form a p-n heterojunction with the hematite substrate as an n-type semiconductor,and promote the charge separation of the carriers improves the PEC performance of the photoanode.In addition,in this paper,hematite nanorods were prepared on FTO glass by hydrothermal method,and then P-doped by post-phosphorization treatment.The cobalt aluminum layered double hydroxides?CoAl-LDHs?was further applied by drip coating compound with it.Then through a series of characterization testing methods,the effects of non-metal P doping and CoAl-LDHs on the water oxidation performance of hematite photoanode PEC were studied.The results show that P anion doping significantly increases the carrier density of hematite and accelerates the charge transfer.Furthermore,the electronic structure change caused by P anion doping can remove part of the surface trap sites of hematite and reduce the surface charge capture.CoAl-LDHs promoter can significantly improve the kinetics of water oxidation of hematite,effectively passivate the surface defects of P-Fe₂O₃,and reduce the recombination of surface charges.Moreover,during the water oxidation process,the conversion of low-cost Co ions to high prices can effectively improve the injection efficiency of holes,thereby further improving the PEC performance of the hematite photoanode.At 1.23V vs.RHE,the photocurrent density of the CoAl-LDHs/P-Fe₂O₃ composite photoanode can reach 1.56 m A cm^-2,which is 1.6 times higher than that of a single hematite,and the starting potential is negatively shifted by100 mV.