Constructionand Performance Optimizationof Photoelectrochemical Energy Conversion System Basedon Perovskite-type Ferroelectric BiFeO₃

The development and improvement of cost-effective photoelectrochemical energy conversion materials is one of the effective ways to solve the current energy shortage and environmental pollution.Among many photoelectrochemical energy conversion materials,the perovskite-type ferroelectric material Bi Fe O₃has attracted people's attention due to its narrow band gap and low cost.Importantly,the spontaneous polarized electric field of ferroelectric materials can facilitate carrier separation,and the anomalous photovoltaic effect of ferroelectric materials can make the photovoltaic voltage of the device independent of the band gap.However,due to the relatively poor photoelectrochemical energy conversion efficiency of Bi Fe O₃,it cannot meet the actual needs of people,which severely limits its application in industry.Therefore,the modification of Bi Fe O₃-based photoelectrochemical energy conversion materials has always been a hot research topic.This paper focuses on the problems of low photoelectrochemical energy conversion efficiency and limited application in the field of photoelectric catalysis of Bi Fe O₃.From the point of view of improving the charge separation efficiency,designing and preparing high-efficiency photoelectrocatalytic materials and applying them to the fields of photoelectrochemical water splitting and photocatalysis.They are modified with precious metal Au,non-precious metal oxide Cu₂O and non-metallic g-C₃N₄respectively,and at the same time cooperated with the ferroelectric polarization field accelerates the separation and migration of electron-hole pairs,improves the photoelectrochemical energy conversion performance of Bi Fe O₃,and promotes the large-scale application of perovskite-type ferroelectric materials in the field of photoelectric catalytic water splitting.The specific research contents are as follows:(1)In this article,we prepared FTO/Bi Fe O₃and FTO/Au/Bi Fe O₃photoelectrodes and applied them to photoelectrochemical water splitting.After the introduction of the Au buffer layer,the photocurrent density increased from-12?A cm^-2to-36?A cm^-2(-0.4 V vs Ag/Ag Cl),and the monochromatic incident photon-to-electron conversion efficiency increased from 6.6%to 16.4%.Experimental and theoretical analysis shows that the Au buffer layer plays a positive role in promoting carrier migration,reducing the recombination of electrons and holes,and reducing charge transfer resistance.(2)Constructing a heterojunction is one of the effective means to improve the photoelectrochemical energy conversion efficiency of semiconductors.In this article,we use magnetron sputtering to deposit Cu₂O on the surface of the Bi Fe O₃film to construct a Bi Fe O₃/Cu₂O heterojunction.Experiments show that heterojunction plays an important role in improving light absorption and promoting photo-generated electron-hole pair separation.In addition,the ferroelectric polarization field will further increase the photocurrent density of the photoelectrode,reflects the significant advantages of ferroelectric materials in photoelectrochemical water splitting,and provides ideas for the design of high-performance photoelectrochemical energy conversion systems.(3)Traditional heterojunctions still have some limitations in the application of photoelectrocatalysis.For this reason,a direct Z-scheme Bi Fe O₃/g-C₃N₄heterostructure catalyst with high redox capacity was prepared.The photocatalytic performance of the photocatalyst was evaluated by the degradation of methyl orange under light.Compared with the original catalyst,the catalytic rate of the Z-scheme heterostructure catalyst was faster,and after polarizing the catalyst,the photocatalytic performance was further improved.The mechanism of catalyst performance improvement was studied,and the charge transfer path in Z-scheme heterojunction was discussed in detail through photodeposition and electron spin resonance tests.Ferroelectric polarization and Z-scheme heterojunction synergistically promote the performance of Bi Fe O₃-based photocatalysts,which provides a feasible way for us to prepare high-performance photocatalysts using ferroelectric materials.