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

非技术描述：有效地将阳光和水转化为氢是一种生产“绿色”燃料的有吸引力的方法，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，以及能够解决工程挑战的人力资本的发展。几十年来，人们已经知道有各种各样的催化剂可以进行光解（将水转化为氢），但许多催化剂仍然效率低下或价格昂贵，无法用于商业应用。光催化剂的性能可以通过控制其电子结构得到最有效的改善，而电子结构取决于诸如颗粒大小、形状、化学性质、缺陷结构或与邻近材料的相互作用等变量。由此产生的光催化性能通常表征为数百万个粒子的集合，其单个性质可能会有显着变化。对整个系统进行平均掩盖了纳米粒子水平上电子性质和光催化性能之间的基本关系。该项目开发并利用了新的方法来测量单个纳米粒子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体验，将研究和教育结合起来，同时促进多样性。它将使伊利诺伊州的教师能够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，通过与伊利诺斯州工程教育创新铸造厂（Foundry for Innovation in Engineering education）密切合作，将促进基于探究和主动学习的教育方法。这种多方面的方法将对STEM管道的各个层面产生影响。技术细节：该项目旨在为优化的高效低成本异质结光催化剂的纳米结构设计提供改进的科学基础。单个异质结纳米线的电子特性和光催化性能被表征为尺寸的函数。实验利用一种几何结构，可以进行电测量，非原位结构和化学表征，随后通过环境透射电子显微镜（TEM）进行原位光催化。原位透射电镜提供了适当的空间分辨率、时间分辨率和几何灵活性，以量化光催化气体在单个纳米结构中的演化速率。特别强调的是阐明表征缺陷和缺陷状态在影响单个纳米级光催化剂性能变化中的作用。实验的目标是ZnO-Pt和ZnO-Fe2O3，它们将作为模型氧化物-金属和模型低成本氧化物-氧化物体系，展示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.