Research On Preparation,Modification And Piezoelectric Photoelectrochemicial Performance Of Bi₂WO₆ Photoelectrodes

In the research field of solar energy photoelectrochemial water splitting for hydrogen production,piezoelectric photoelectrochemial water splitting,which directly promotes the carrier separation efficiency through the piezoelectric electric polarization electric field of the material itself,is one of the most promising ways to achieve efficient solar energy conversion efficiency.Among many semiconductor materials,bismuth tungstate（Bi₂WO₆）has attracted much attention due to its good chemical stability,moderate conduction band position,and good piezoelectric response.However,the further development of Bi₂WO₆ in the field of piezoelectric photoelectrochemial water splitting is limited by its low polarization electric field intensity and narrow light response range.Therefore,studying the modification of Bi₂WO₆ photoelectrode to regulate its carrier transport process and polarization electric field intensity is the key to improving the piezoelectric photoelectrochemial performance of Bi₂WO₆.This article synthesized Bi₂WO₆ photoelectrodes with different morphologies through hydrothermal and solvothermal methods,and analyzed the mechanism of the influence of micro morphologies on their piezoelectric photoelectrochemial performance.W⁵⁺ion doped Bi₂WO₆ photoelectrode was prepared using the method of element doping modification,and the effect and mechanism of W⁵⁺ion doping on the piezoelectric photoelectrochemial performance of the photoelectrode were studied.Finally,lattice fluorine and adsorbed fluorine were introduced into the Bi₂WO₆photoelectrode through surface fluorination treatment,and the influence mechanism of lattice fluorine and adsorbed fluorine on the piezoelectric effect,carrier separation efficiency,and piezoelectric photoelectrochemial performance of Bi₂WO₆ was analyzed.The results showed that the photocurrent of the nano plate Bi₂WO₆-P prepared by solvothermal method reached 0.078 m A/cm²（1.23 V vs.RHE）under the condition of illumination and 90 k Hz,1.3 times that of the Nanoflower Bi₂WO₆-H prepared by hydrothermal method.This is attributed to the fact that the piezoelectric built-in electric field can effectively promote the separation of photo generated charge carriers,and the vertically staggered nanoplate structure is more conducive to charge separation and transmission.By adjusting the concentration ratio of precursor W element,W⁵⁺was successfully introduced into Bi₂WO₆.Under illumination and 90 k Hz ultrasound conditions,the photocurrent density of Bi₂WO₆-2 photoelectrode（Bi:W=1:1 in precursor solution）reached 0.181 m A/cm²,which was 1.2 times higher than the original electrode.This is because W⁵⁺can not only broaden the optical response range of Bi₂WO₆,but also improve the driving effect of the built-in electric field generated by Bi₂WO₆ piezo electric polarization on the photogenerated charge,thereby improving its piezoelectric photocatalytic performance.By fluorination treatment,lattice fluoride and adsorbed fluoride were introduced into the Bi₂WO₆ photoelectrode.Under an applied voltage of 1.23 V vs.RHE,the photocurrent density of Bi₂WO₆-F_1.0 reached 0.218m A/cm²,which is 2.9 times that of the original electrode.And after introducing ultrasound conditions,the photocurrent density reached 0.298 m A/cm²,which is 3.3times that of the original electrode.Through analysis,it can be concluded that fluoride ions replace some oxygen ions in the lattice,increasing the strength of the built-in electric field in Bi₂WO₆ piezoelectric materials.At the same time,the adsorption of fluorine on the surface of the material leads to the generation of surface charge traps,which further reduces the recombination of surface charges under the influence of surface piezoelectric potential,thereby effectively improving the piezoelectric photoelectrochemial performance of Bi₂WO₆ photoelectrode.