目前，传统能源的储备越来越少，寻找和利用适合时代发展的绿色能源成为科学家探讨的热点。绿色、干净、易制备的氢能源在近些年来引起了人们的关注，因此利用半导体制氢成为了科学家们研究的重点。半导体由于特殊的能带结构，能够激发出光生载流子进而参与材料表面的析氢或析氧反应，但会受到光电催化制氢反应体系的一些限制。由于铁电体的自发极化能够改善光生载流子的迁移，进而提高光电催化反应效率，因此寻找、制备并且利用具有合适能带结构的铁电体作为光电极来光电催化制氢成为一项挑战。

本文以BiFeO₃薄膜为研究对象，首先分析了铁电极化大小和方向对光生载流子迁移的影响，越大的极化强度越能促进光生电荷的迁移，而极化方向会影响光生电荷迁移的方向。然后，我们通过在BiFeO₃薄膜表面修饰羟基来提高材料的光电催化活性，发现这能够使能带弯曲发生偏移从而促进光生载流子迁移，并且在薄膜表面形成新的高活性反应位点来促进水的氧化还原反应。最后，通过在表面修饰羟基和制备周期性铁电畴使BiFeO₃薄膜具备铁电超畴结构，这能够大大提高薄膜的光电催化效率，使BiFeO₃薄膜具备优异的光电催化性能，同时能够使BiFeO₃薄膜既作为光阴极来促进析氢反应，也可以作为光阳极来促进析氧反应。本文的研究能够对调控表面/界面结构来影响铁电体的表面功能提供新的见解，也为制备基于铁电材料的高效光电催化水分解的双功能光电极提供新的策略。

Now that energy reserves are getting less and less, seeking and utilizing green energy suitable for the development of the times has become a hot topic for scientists. Green, clean, and easy-to-prepare hydrogen energy has already aroused people's attention recently. Therefore, the use of semiconductors to produce hydrogen has become the focus of research by scientists. Due to the special energy band structure of semiconductors, photo-generated carriers can be excited to participate in the hydrogen evolution or oxygen evolution reaction on the surface of the material, which are subject to some limitations of the photoelectrocatalytic hydrogen production reaction system. The spontaneous polarization of ferroelectrics can improve the migration of photo-generated charges and improve the efficiency of photoelectrocatalytic reactions. Therefore, it is a challenge to find, prepare and use ferroelectric with suitable band structure as the photoelectrode for photoelectrocatalytic hydrogen production produce.

In this paper, BiFeO₃ thin films were studied. Firstly, we analyzed the effects of the magnitude and direction of ferroelectric polarization on the photo-generated carriers’ migration. The greater the polarization intensity, the more it promotes the transfer of photo-generated charges, the polarization direction will affect the direction of photo-generated charges migration. Then, we improved the photoelectrocatalytic activity of the BiFeO₃ thin film by modifying hydroxyl groups on the material’s surface, which can cause the band bending to be offset for promoting the migration of photo-generated carriers and form new highly active reaction sites on the surface of the film to promote the redox reaction of water. Finally, BiFeO₃ thin film with ferroelectric super-domains structure can be prepared by modifying hydroxyl groups on the surface and preparing periodic ferroelectric domains, which can greatly improve the photoelectrocatalytic efficiency of the thin film, so that the BiFeO₃ film has excellent photoelectric catalytic performance. The BiFeO₃ film with ferroelectric super-domains structure can be used as a photocathode to promote hydrogen evolution reaction and photoanode to promote oxygen evolution reaction. The research in this paper can provide new insights into the regulation of surface/interface structure to influence the surface functions of ferroelectrics, and also provide new design ideas for the preparation of bifunctional photoelectrode based on ferroelectric materials with high-efficiency photoelectrocatalytic water splitting.