黑硅光催化制氢电极的陷光结构与载流子复合输运规律研究

Silicon is an earth-abundant semiconductor that dominates the world photovoltaic industry and is an equally promising material for the Photoelectrochemical (PEC) production of H2 at Si/electrolyte interfaces. Si has a band gap well-matched to the solar spectrum and a conduction band edge position more negative than the hydrogen evolution reaction potential for water reduction. One problem with a planar water-silicon interface is that about 25% of incident photons are reflected away from the silicon surface. To maximize conversion of solar energy to H2 fuel, a low reflectance Si surface is required. Recent efforts have made great improvement on the anti-reflection of the Si surface through the formation of light-trapping structures such as Si nanowires and black Si surface. On the other hand, improving the carrier separation and collection is essentially significant for acquiring highly efficient Si nanostructure based photoelectrodes interfacing with liquid electrolyte as an alternative format of solar cells. The surface defect, impurities, surface physical chemistry and Si interface have a great impact on the carrier separation and collection. But few efforts have been made especially on this spot. In this project, The planned research activities aim at 1) fabricating light-trapping structures (such as Si nanowires, nanotubes and pyramidal structures) using chemical and physical methods (such as metal assisted corrosion and plasma enhanced erosion) and Si\oxides interfaces (such as Si\TiO2, Si\Al2O3) using chimice-douce and magnetron sputtering methods; 2) Understanding of the relationship between the catalytic activities and the features (such as crystal facet, structure, morphology, surface area, surface absorption and deposition process) of the light-trapping structures and Si\oxides interfaces and then developping new robust hydrogen production systems. Trough the investigation, the dependence of the catalytic activities on the features of the Si surface and interface could be found. Our research results will present in more than 5 peer-reviewed journals of high impact. Our research activities have the potential to be of high interest for developing next-generation environmentally friendly energy conversion devices.

硅由于具有合适禁带宽度，可吸收大部分的太阳光，是广泛使用的光电转换材料。在硅/电解液界面利用光催化作用制取氢气是制氢研究的热点之一。对于使用硅基光催化电极制氢而言，高效吸收光能和将光生载流子输运到硅界面是提高光催化效率的关键。但由于约25%的光吸收损失在反射上，因此目前最新的研究多通过制备纳米线等黑硅陷光结构降低光反射。而陷光结构的表面缺陷、杂质、表面物理化学状态和硅/氧化物界面层特性都影响载流子复合和输运，但目前很少有这方面的专门研究。鉴于此本项目旨在：1)制备黑硅陷光结构（如纳米线等）和Si/氧化物界面层；2)探明陷光结构和硅/氧化物界面层特性与载流子复合、输运及催化活性之间的关系。从而获得兼具高效吸光特性和低载流子复合速率的光催化电极，且其分解水制氢效率高于10%。并发表学术论文5篇以上。项目研究成果对推动新型"绿色"制氢方式和能源转换器件的研究具有重要的理论实践指导意义。

本项目通过制备低维（一维和二维）纳米结构，围绕纳米结构中的表面物理化学状态、界面层特性和晶面状态，晶体分布等开展以下研究工作： (1) 通过制备高光吸收的黑硅光催化电极，并通过物理沉积等方法制备了Bi2O3/Si p-n结光催化水分解阳极材料；(2) 研究新型低维纳米结构表面、界面微结构和材料的尺寸效应对光催化效率的影响规律，有效地抑制光激发生成的电子和空穴的再复合，提高光催化材料的活性；(3) 获得了兼具高效吸光特性和低载流子复合速率的光催化电极, 同时利用催化效率的影响规律，制备了Bi4Ti3O12、BiOCl、BiOI二维纳米片、Bi2O3/Bi4Ti3O12复合二维纳米片等光催化电极。相关成果发表SCI论文6篇，申请发明专利1项 。