| Energy crisis and environmental pollution are two major challenges facing human society.Photoelectrochemical(PEC)water splitting technology can use semiconductors for converting solar energy to hydrogen and other clean fuels,which is an ideal way to obtain energy in the future.BiVO4 is a semiconductor with visible light response and bandgap of 2.4 e V.It is widely used as a photoanode material for PEC water splitting.Compared with other inorganic semiconductors,its valence band edge position is slightly larger by 1.5 e V than that of water oxidation potential,which makes it easier to produce O2,leading to an efficiency(SHE)of>1.8%for solar to hydrogen conversion.However,the actual performance of a BiVO4 photoelectrode is still limited by visible light response,surface area and carrier recombination.There is a far distance between the current status and commercial application of BiVO4.In this thesis,BiVO4 porous films were prepared by electrophoretic deposition,sol-gel and electrochemical deposition.The PEC cells were constructed to evaluate and reveal the main factors affecting the PEC performance of BiVO4.The main research results are listed as follows:BiVO4 microparticles were prepared by hydrothermal method,and then about several micrometers thick film was prepared by electrophoretic deposition method,and the PEC performance was evaluated.Sintering is conducive to the enhancement of charge transfer between BiVO4 microparticles,leading to a better PEC performance.With an increase of sintering temperature,the photocurrent of BiVO4increases gradually,reaching a photocurrent density of 28.4?A/cm2(at 0.6 VSCEpotential)at 600°C.The spikes appeared in the I-t characteristic plots are due to the poor charge separation of BiVO4 photoanodes,which can be eliminated by applying a forward bias.BiVO4 porous films were prepared by sol-gel method.The effects of coating layer,doping and surface modification on the morphology and microstructure of the BiVO4 films were evaluated by means of XPS,SEM and UV-Vis.The effects of light,film thickness,surface modification and electrolyte composition on the PEC performance of BiVO4 porous films were comprehensively discussed.The results show that:45 mmol/L precursor solution concentration,120 nm film thickness,Co-Pi surface modification can obtain the best PEC performance,reaching a photocurrent value of?3.75 m A/cm2 at 0.6 V vs.SCE potential.The BiVO4 porous films were modified by Mo and W doping,and the effect of doping concentration on the PEC performance of BiVO4 was investigated.It was found that 10 at.%Mo and W doping showed the best PEC performance.The photocurrent of W doped samples was 5.61 m A/cm2 at 0.6 V vs.SCE,while that of Mo doped samples was 5.79 m A/cm2.The reason for the enhancement is that the proper amount of Mo and W doping not only improves the carrier separation and inhibits the carrier recombination,but also enhances the photogenerated hole migration.However,when the dopant content is more than 10 at.%,the carrier migration will be hindered and the recombination loss will be increased with the increase of dopant concentration.On this basis,a PEC sensor based on Mo doped BiVO4 was constructed to achieve the detection of glutathione(GSH).The linear range was 0-1000?M and the detection limit was 59 nm.BiVO4 porous photoanode with"wormlike"morphology was prepared by electrochemical deposition.Only 0.1 mol/L Na2SO4 solution was used as electrolyte,the photocurrent could reach a maximum value of 1.33 m A/cm2(1.23 V vs.RHE).After loading Au particles on the BiVO4 surface,the photocurrent increases significantly and reaches the maximum value(2.46 m A/cm2)when the Au deposition time is 150 s.The enhancement of PEC performance is due to the plasmon enhancement effect of Au,which can enhance the visible light absorption and surface electron-hole separation,and reduce the interfacial charge transfer resistance.It is found that the Au modification facilitates enhancing the H2 production performance of PEC cells from 33.2?mol cm-2 h-1 to 59.5?mol cm-2 h-1. |
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