氧化铁/阀金属纳米阵列复合结构光阳极的构建及光解水应用

Solar water splitting has becoming a hot research in the realm of renewable energy. Among variety of semiconductors, hematite has been shown as one of the most promising water splitting photoanodes for its visible light absorption, high solar-to-hydrogen conversion efficiency, stability and low cost. Unfortunately, short carrier diffusion length, electron-hole recombination as well as other drawbacks of bulk hematite limits its efficiency. There has been remarkable researches and progresses being made in promoting carrier separation efficiency by facilitating electron conductivity as well as hole diffusion to the surface, nevertheless, they are far from the theoretical value of solar-to-hydrogen efficiency. It’s the purpose of this project to find an efficient way to solve the key problems of hematite aforementioned. Briefly, hematite/valve metal nanoarray complex structure is to be constructed. The photo-excited hole in hematite could easily reach to the semiconductor/liquid junction within its diffuse length and electron could be collected and conducted fast throng the metal nanochannel. This 3D nanostructure could not only realize full absorption of incident light, but also improve the carrier separation and quantum efficiency through favorable heterogeneous interface formation, so does to the whole solar-to-hydrogen efficiency. The benefits from this project may provide an efficient solution to the problem that hinder the development and practical application of hematite in water splitting for hydrogen production, moreover, may found general application in tackling charge recombination for most photocatalysts through nanostructure engineering and interface control.

近几年光解水制氢成为新能源领域研究的热点。在众多的半导体材料中，氧化铁具有可见光宽谱响应，理论产氢效率高，稳定性好，成本低等优势，是最具开发潜力的光催化材料。然而，本体载流子迁移困难、电子-空穴极易复合等成为制约其实际应用的主要原因。因此，提高氧化铁载流子迁移能力和分离效率成为一项紧要的研究课题。调研表明，此领域最新研究进展与理论效率仍存在巨大差距。本项目旨在提出一条新颖的思路解决上述难题，拟构建氧化铁/阀金属纳米阵列复合结构，该三维结构实现高效光捕获吸收的同时，极大减小载流子在氧化铁本体迁移距离，加速电子导出；此外，该体系氧化铁/阀金属特殊异质界面的构建可实现载流子高效分离和高量子产率，进而从整体上提升光解水制氢效率。本项目的设立和开展有望针对氧化铁实际应用的瓶颈提供一条高效的解决方案；同时，复合结构的设计和界面研究还有助于解决半导体光催化过程载流子易复合等普遍问题，具有普适价值。

针对氧化铁光催化材料本体载流子迁移困难、电子-空穴极易复合等严重制约其光解水效率提升的瓶颈问题，本项目提出通过构建氧化铁/金属钛纳米阵列复合结构减小载流子迁移距离，加速电子-空穴分离，促进光解水效率的提升。氧化铁/钛纳米阵列复合结构光电流在1.23 V vs RHE是单一氧化铁薄膜的5倍以上，饱和光电流达到4.5 mA cm-2, 机理研究表明这主要得益于复合结构本体高电导率促进光生载流子快速迁移和高效分离。接着，通过水热法在氧化铁表面原位掺杂钛金属离子，将氧生成过电势从1.01 V降低到0.48 V vs RHE, 解决了氧化铁氧生成过电势高的缺点，机理研究表明钛离子掺杂大幅度增强界面电荷传输和光电压，提高了氧生成的反应动力学。此外，制备的具有宽域、高光吸收且稳定的镍纳米颗粒，为增强半导体光吸收及通过局域热增强效应提高光解水速率提供新途径。以上成果达到了项目预期，对于接下来进一步设计出高效全电极光解水器件具有重要的科学参考价值；同时，该思路还有助于设计非氧化铁类半导体/金属钛复合结构光催化剂用于高效光解水产氧产氢，具有普适价值。