CAREER: Scale Dependent Property-Performance Relationships in Individual Heterojunction Nanowire Photocatalysts

非技术描述：高效地将阳光和水转化为氢气是生产“绿色”燃料的一种有吸引力的方法，可以帮助支持未来的美国经济。 商业上实现这一目标需要提高对相关过程的科学理解，并开发能够应对工程挑战的人力资本。 几十年来，人们已经知道各种催化剂可以进行光解（将水转化为氢气），但许多催化剂对于商业应用来说效率太低或太昂贵。 光催化剂的性质可以通过控制它们的电子结构来最有效地改善，电子结构取决于诸如颗粒尺寸、形状、化学、缺陷结构或它们与相邻材料的相互作用等变量。所得到的光催化性能通常在数百万个颗粒的集合上表征，这些颗粒的个体性质可以显著变化。 在整个系统的平均模糊的电子性质和光催化性能之间的基本关系，在纳米粒子的水平。 该项目开发和利用新的方法来测量单个纳米颗粒的电子特性和光催化性能，以提高对尺寸，缺陷和界面对电子结构和相关光催化性能的影响的科学理解。 该活动通过教育专业项目的研究经验整合了研究和教育，同时促进了多样性。 它将使伊利诺伊州的教师将真实的科研经验带入K-12课堂，为本科生提供研究经验，并为研究生提供研究支持。 此外，基于探究和主动学习的教育方法将通过与伊利诺伊州工程教育创新铸造厂（IFoundry）密切合作来培养。 这种多方面的方法将对STEM管道的各个层面产生影响。技术支持：该项目旨在为优化高效低成本异质结光催化剂的纳米结构设计开发更好的科学基础。 单个异质结纳米线的电子性质和光催化性能被表征为尺寸的函数。 该实验利用的几何形状，使电气测量，非原位结构和化学表征，并随后在原位的环境透射电子显微镜（TEM）。 原位TEM提供了适当的空间分辨率，时间分辨率和几何灵活性，量化在单个纳米结构的光催化气体的演变率。 特别强调的是被放置在阐明的作用，影响个别纳米级光催化剂的性能变化的特征缺陷和缺陷状态。 该实验的目标ZnO-Pt和ZnO-Fe 2 O3，这将作为模型氧化物-金属和模型低成本氧化物-氧化物系统，表现出所需的物理和满足实验要求。

NON-TECHNICAL DESCRIPTION: Efficiently converting sunlight and water into hydrogen is an attractive approach to producing 'green' fuels that could help support the future US economy. Commercially realizing this goal requires improved scientific understanding of the associated processes and the development of human capital capable of addressing the engineering challenges. A variety of catalysts have been known to perform photolysis (converting water to hydrogen) for several decades, but many remain too inefficient or expensive for commercial application. The properties of photocatalysts may be improved most effectively by controlling their electronic structure, which depends on variables such as particle size, shape, chemistry, defect structure, or their interactions with adjoining materials. The resultant photocatalytic performance is typically characterized over an ensemble of millions of particles, whose individual properties could vary significantly. Averaging over the entire system obscures the fundamental relationships between the electronic properties and the photocatalytic performance at the nanoparticle level. This project develops and utilizes new approaches to measuring the electronic properties and photocatalytic performance of individual nanoparticles in order to develop improved scientific understanding of the effects of size, defects, and interfaces on both the electronic structure and the associated photocatalytic performance. The activity integrates research and education through a research experience for education majors program while promoting diversity. It will enable Illinois teachers to bring authentic scientific research experience into the K-12 classroom, research experience for undergraduate students, and research support for a graduate student. As well, inquiry-based and active-learning approaches to education will be fostered by working closely with the Illinois Foundry for Innovation in Engineering Education (IFoundry). This multifaceted approach will have impact at all levels of the STEM pipeline. TECHNICAL DETAILS:The project is seeking to develop improved scientific underpinnings for nanostructural design of optimized high-efficiency low-cost heterojunction photocatalysts. The electronic properties and photocatalytic performance of individual heterojunction nanowires are being characterized as a function of size. The experiments utilize a geometry that enables electrical measurements, ex situ structural and chemical characterization, and subsequent in situ photocatalysis by environmental transmission electron microscopy (TEM). In situ TEM provides appropriate spatial resolution, temporal resolution, and geometric flexibility necessary to quantify the rate of photocatalytic gas evolution at individual nanostructures. Special emphasis is being placed on elucidating the role of characterized defects and defect states in affecting the variation in performance of individual nanoscale photocatalysts. The experiments target ZnO-Pt and ZnO-Fe2O3, which will serve as model oxide-metal and model low-cost oxide-oxide systems that exhibit the desired physics and fulfill experimental requirements.