窄禁带半导体光解水电极的三维纳米构筑及表面薄膜修饰

Semiconductors with narrow band gaps (e.g. Si) have shown great potentials for efficient solar water splitting. However, these materials suffer from photocorrosion in contact with aqueous electrolytes. Besides, nanostructuring may introduces surface defects to these materials. This proposal aims to develop a novel nanostructure fabrication strategy based on glancing angle deposition (GLAD) and chemical etching. This strategy could balance the nanostructuring with surface defect control, obtaining three-dimensional (3D) nanostructured photoelectrodes that could simultaneously suppress light reflection and promote bubble detachment from the electrode surface. Using atomic layer deposition (ALD) as an effective tool to deposit protective layer onto the surface of 3D nanostructures, together with a thorough investigation of the adsorption and reaction mechanism of precursor molecules in the nano-pores or nano-channels, we could clarify the nucleation and growth models of thin films on the surface of the high aspect ratio nanostructures, and consequently fabricate high-quality protective layer that is uniform, dense and pinhole-free. Thus, Si and other corrosion vulnerable electrodes could be protected against the harsh condition of solar water splitting process. Furthermore, the relationship between charge transfer/recombination and structure of semiconductor/overlayer interface could be revealed by precise time-resolved spectroscopy techniques such as time-resolved fluorescence. This would be a guidance for optimizing the crystal and interface structure of the protective layer so that it could passivate the surface defects of 3D nanostructures. On the basis of the above results, highly stable and efficient corrosion-resistant photoelectrodes based on narrow bandgap semiconductor could be obtained for solar water splitting.

基于窄禁带半导体（如Si）的光解水制氢有望获得较高的光能转化效率。然而此类材料在电解液中易被腐蚀，且对其进行纳米构筑常会引入表面缺陷。本项目将发展基于掠角沉积（GLAD）和化学蚀刻的新型纳米结构制备方法，使纳米形貌的构筑与表面缺陷位的调控达到平衡，获得可以有效抑制光反射并促进气泡脱附三维纳米结构电极。通过原子层沉积（ALD）在该三维纳米结构表面制备保护层薄膜，并研究ALD前驱体分子在纳米孔道内的扩散、吸附、反应机制，阐明薄膜在高长径比纳米结构中的成核与生长规律，获得均匀、致密、无孔道的高质量保护层，使Si等易腐蚀半导体耐受严苛的光解水条件。在此基础上，基于瞬态荧光光谱等高时空分辨技术，揭示保护层/半导体表界面的微观电荷传导/复合机制和表界面微观过程；并以此指导对保护层晶型结构和界面结构的优化，使其具有电荷传递和表面缺陷修复的双重作用。最终获得稳定、高效的耐腐蚀窄禁带半导体光解水电极。

光催化水分解制氢将太阳能转换为氢能，是解决能源危机和环境问题的重要途径之一。本项目基于Si、CIGS、BiVO4、Fe2O3等窄禁带半导体材料，借助原子层沉积（ALD）、掠角沉积（GLAD）、磁控溅射沉积等可控制备手段，构筑了具备三维纳米形貌的光电极，进一步通过修复光电极表、界面缺陷位，构建了光生电荷的高效传输通道，提升了光生载流子寿命及光电极内建电场强度，综合提升光解水制氢效率及光电极稳定性。例如，在CIGS电极中提出“两步镀铂法”来独立调控Pt助催化剂的空间分散度和粒径，综合提升了CIGS电极产氢效率。在单晶Si电极中提出“双面钝化”的表界面修饰策略，消除金属诱导的界面缺陷态和单晶Si表面悬挂键，实现了当前最高的光催化水分解制氢效率。本项目在J. Am. Chem. Soc.、Angew. Chem. Int. Ed.、Energy Environ. Sci.、Adv. Mater.、Chem. Sci.、Small等重要国际SCI期刊上发表论文23篇，其中2篇入选ESI高被引论文，8篇被选为封面（扉页）论文，并应邀为Chem. Soc. Rev.撰写综述2篇。研究成果4次被Chemeurope和Chemistry Views（Wiley）等国际学术媒体报道。