Study On Preparation And Photoelectrochemical Properties Of Nano-porous BiVO₄ Composite Materials

Photoelectrochemical?PEC?water splitting is one of the effective ways to resolve energy crisis and environmental problems.In the PEC process,the PEC performance is mainly determined by the semiconductor photocatalytic materials,thus it is important to develop the semiconductor materials with excellent stability and high utilization of solar energy.Among all the available semiconductor materials,BiVO₄ has emerged as an attractive candidate for PEC photoanode materials due to the suitable ban gap?2.4-2.6 eV?,stable chemical performance,environment-friend and low cost.However,there are some defects such as easy recombination of photo-generated electron-hole pairs and low migration rate of photon-generated carrier,which limits its efficiency and application.Aiming at these defects,this study was performed to improve the PEC properties of BiVO₄ by constructing heterojunction and sensitizing quantum dot.The main research contents are as follows:?1?CdS/BiVO₄ heterojunction was successfully synthesized on the FTO-coated glass substrate through electrodeposition-annealing followed by the second electrodeposition.PEC measurements were performed with CdS/BiVO₄ heterojunction.The result shows that,after CdS loaded on BiVO₄,the photoelectrochemical density of CQDs/BiVO₄ electrode at 0.4 V?vs Ag/AgCl?bias potential is about 4.2 times of that of bare BiVO₄ electrode.This is attribute to expand the response of visible light and the formation of heterojunction between CdS and BiVO₄,which leads to effective separation of charge carriers and prevents the recombination of photo-generated electron-hole pairs.?2?Using nano-porous Bi VO₄ as a substrate,the carbon quantum dots?CQDs?was loaded onto BiVO₄.The photoelectrochemical properties and photoelectrochemical detection for sodium nitrite?NaNO₂?of BiVO₄ and CQDs/BiVO₄ were studied.The result shows that the light absorption intensity of composite enhanced and the interfacial charge transfer resistance decreased.Under optimum conditions,the electrodes were used to detect NaNO₂,the sensitivity of the CQDs/BiVO₄ electrode reaches 413.9?A(mmol^-1)^-1 cm^-2,which is about 2 times of 157.2?A(mmol^-1)^-1 cm^-2 for BiVO₄ electrode.The linear range of the CQDs/BiVO₄ electrode is 4-1050?mol L^-1,while the BiVO₄ electrode is 48-1050?mol L^-1.The detection limit of the CQDs/BiVO₄ electrode is 3.57?mol L^-1?S/N=3?,lower than 6.69?mol L^-1 of the BiVO₄electrode.The result reveals the effective separation of photogenerated carriers and electronic transmission of CQDs/BiVO₄ electrode is higher than BiVO₄ electrode.