基于内建电场三维硅纳米结构的α相三氧化二铁制备及其光催化性能的研究

The increasing serious global power and environmental crisis have become the twomain problems which the human being has to face during the process of continuous development for the society. It is an inevitable tendency to develop a new kind of new energy with good performance, long cycling life, no pollution and low price, therefore looking for a large reserve, clean new energy has risen to the world's agenda. Semiconductor-based solar-driven water splitting has attracted a significant attention over the last years and considered as alternative way to solve these problems.. Wide band-gap metal oxide semiconductors have been extensively explored as water oxidation photocatalysts. Yet, the inability of these materials to absorb light in the visible range of the solar spectrum has greatly limited their water splitting efficiency. As a common and inexpensive semiconductor on earth, hematite has emerged as a promising photoanode for solar water oxidation due to its excellent intrinsic stability, environmental compatibility, and favorable band-gap energy (~1.9-2.3 eV) capable of 12.9-16.8% solar-to-chemical fuel efficiency. However, recent studies have offered little optimism for hematite photoanodes, because low solar-to-chemical conversion efficiencies have only been achieved and large overpotential is needed for water splitting, primarily due to short minority carrier diffusion length, low absorption coefficient, and sluggish oxygen evolution kinetics at hematite surface. Here we aim to develop a new silicon-hematite core-shell structure which is based on build-in electric filed. The function of build-in electric filed and the behavior of short-life carrier will be studied in this project. To realize this goal, we plan to experiment as following: (1) silicon nanowires will be fabricated by metal-catalyzed chemical etching method and hematite coated on SiNWs will be prepared by thermal-decomposition. Then the structure will be optimized to improve the performance of solar-driven water splitting; (2) the build-in electric field will be fabricated by thermal-diffusion and the back layer will be planned to treated by high-concentration Al doping or passivated by aluminum trioxide to from n+pp+ junction or back-passivated pn junction. The effect of build-in electric field will be studied and the system will be optimized according to the experiments. (3) we will try to find a matching photocathode and compose a whole water splitting system with hematite. . To conclude the study，we will solve these problems such as short minority carrier diffusion length, low absorption coefficient, and sluggish oxygen evolution kinetics and develope a build-in electric field based visible light drive water splitting system.

半导体光催化分解水是应对日益严重的能源危机的一种重要方法，三氧化二铁是一种非常有应用前景的光催化剂。但是三氧化二铁固有的电子迁移率低、光生载流子扩散距离短、光吸收系数小等缺陷仍然是实现三氧化二铁光催化分解水技术突破的瓶颈。本项目以硅-三氧化二铁核壳结构为研究对象，采用内建电场的方法，研究内建电场在这种光催化体系中的作用、对载流子行为及反应动力学的影响，得到高效三氧化二铁光分解水体系，同时阐明其作用机制。研究内容包括：（1）硅纳米线模板热分解制备三氧化铁光催化性质的研究；（2）硅纳米线内建电场对三氧化二铁光阳极催化性能的影响；（3）三氧化二铁光催化全分解水的研究。本项目的结果将解决三氧化二铁材料在光催化应用时光吸收差、电荷输运能力差、载流子易复合等缺点，同时构建一个基于硅纳米结构内建电场的光分解水体系，对硅-三氧化二铁复合结构光电化学性质研究提供有益的理论和技术指导。

半导体光催化分解水是应对日益严重的能源危机的一种重要方法，三氧化二铁是一种非常有应用前景的光催化剂。但是三氧化二铁固有的电子迁移率低、光生载流子扩散距离短、光吸收系数小等缺陷仍然是实现三氧化二铁光催化分解水技术突破的瓶颈。本项目以硅-三氧化二铁核壳结构为研究对象，采用内建电场的方法，研究内建电场在这种光催化体系中的作用、对载流子行为及反应动力学的影响，得到高效三氧化二铁光分解水体系，同时阐明其作用机制。.研究内容包括：（1）硅纳米线模板热分解制备三氧化铁光催化性质的研究；（2）硅纳米线内建电场对三氧化二铁光阳极催化性能的影响；（3）三氧化二铁光催化全分解水的研究。本项目的结果将解决三氧化二铁材料在光催化应用时光吸收差、电荷输运能力差、载流子易复合等缺点，同时构建一个基于硅纳米结构内建电场的光分解水体系，对硅-三氧化二铁复合结构光电化学性质研究提供有益的理论和技术指导。.项目实际发表第一标准SCI论文超过20篇，申请发明专利超过10件，参加项目的5名硕士研究生全部按期毕业，项目执行期间共有三名硕士研究生获国家奖学金。.发表在催化领域国际权威期刊《应用催化B》上的《Ultrafine Rh nanocrystals decorated ultrathin NiO nanosheets for urea electro-oxidation》论文主要在碱性介质中，阳极尿素氧化反应（UEOR）是碱性尿素燃料电池，富尿素废水处理和尿素增强水解等过程中关键的半反应之一，因此对UEOR的研究对可持续能源转化和环境保护具有重要的意义。而镍基电催化剂也因其成本低廉，活性和贵金属相当的优势备受关注。该工作采用氰胶-硼氢化钠法以及高温处理成功制备出铑微晶修饰的厚度仅为1.6nm的氧化镍超薄纳米片（Rh-NCs/NiO-NSs）复合电催化剂。Rh-NCs均匀分散在NiO-NSs上，可以显著促进NiIIIOOH活性物种的产生，加速CO分子的氧化，抑制镍基催化剂的中毒现象，促进尿素的电催化氧化。与NiO-NSs相比，Rh-NCs/NiO-NSs表现出更强的电催化活性和高稳定性，成为碱性尿素燃料电池，富尿素废水处理和尿素增强水解等应用中极具潜质的电催化剂。