Heterogeneous Catalysis on Plasmonic Metallic Nanostructures: Selective Catalytic Conversion at Lower Temperatures co-Driven by Solar and Thermal Energy

在这个由化学系化学催化计划资助的项目中，密歇根大学教授苏尔乔·林尼克(Ann Arbor)正在开发利用太阳能驱动化学转化的新一代光催化剂。这些新的光催化剂是银、铜和金的小纳米颗粒，一方面具有与太阳光的强烈相互作用(即，它们聚集了太阳能)，另一方面具有高的化学活性(即，激活了一些所需的化学转化)。这一新一代光催化剂将补充这一领域传统使用的半导体光催化剂。林尼克教授为当地高中开发了一个外展项目，让当地高中生有机会参与这项研究，了解可持续能源转换。这项工作的更广泛影响包括发现新一代光催化剂的潜在社会效益，以及为学生和教师开发培训机会。最近的研究表明，在弱光照射下，等离子体金属纳米粒子能够以有意义的速率激活电子驱动的化学反应。等离子体纳米结构(使用的是银、金和铜)与扩展的金属表面(金属块体)的根本不同之处在于，它们通过局域表面等离子体共振(LSPR)与UV-Vis光发生强烈的共振作用。虽然这些初步研究为等离子体金属的光化学领域带来了一个非常活跃的领域，但仍有许多关键问题没有得到解答。该项目侧重于其中的一些问题，包括确定：(1)等离子体将高能电子转移到吸附体并在此过程中引发化学转变的机制；(2)所报告的反应速度与光强之间的非线性依赖关系的机制；以及(3)等离子体金属纳米颗粒上观察到的光化学的活性中心的性质。解决这些问题对于发展金属纳米颗粒的光学性质、它们的几何结构(在单个颗粒和团簇水平上)和它们的光催化活性之间的预测关系至关重要。这对于我们理解在这些材料上发生的表面光化学，控制这些过程的程度，以及影响最佳光催化系统设计的参数是很重要的。

In this project funded by the Chemical Catalysis program of the Chemistry Division, Professor Suljo Linic of The University of Michigan (Ann Arbor) is developing a new generation of photocatalysts that use solar energy to drive chemical transformation. These new photocatalysts are small nanoparticles of silver, copper and gold, which are on one hand characterized by their strong interaction with solar light (i.e., these concentrate the solar energy) and on the other hand by their high chemical activity (i.e., activate a number of desired chemical transformations). This new generation of photocatalysts will complement semiconductor photocatalysts, which are traditionally used in this field. An outreach program developed by Professor Linic to area high schools is allowing local high school students the opportunity to participate in this research and to learn about sustainable energy transformations. The broader impacts of this work include potential societal benefits from the discovery of new generation of photocatalysts as well as the development of training opportunities for students and teachers. It was demonstrated recently that when illuminated with low intensity light, plasmonic metal nanoparticles can activate electron-driven chemical reactions at meaningful rates. The characteristic of plasmonic nanostructures (Ag, Au, and Cu were used) that makes them fundamentally different than extended metal surfaces (metal bulk), is their strong resonant interaction with UV-vis light through the excitation of localized surface plasmon resonance (LSPR). While these initial studies led to a very vibrant field of photochemistry on plasmonic metals, there are many unanswered critical issues. The project focuses on a number of these issues, including identification of: (i) the mechanism by which plasmons transfer energetic electrons to the adsorbates and in doing so induce chemical transformations, (ii) the mechanisms responsible for the reported non-linear dependency between reaction rate and light intensity, and (iii) the nature of the active sites responsible for the observed photochemistry on plasmonic metal nanoparticles. Addressing these issues is critical for the development of predictive relationships between optical properties of metal nanoparticles, their geometric structure (at the single particle and a cluster level), and their photocatalytic activity. This is important for our understanding of the surface photo-chemistry taking place on these materials, the extent to which these processes can be controlled, and the parameters that influence the design of optimal photo-catalytic systems.