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

在这个由化学部化学催化计划资助的项目中，密歇根大学（安阿伯）的Suljo Linic教授正在开发新一代的光催化剂，利用太阳能来驱动化学转化。这些新的光催化剂是银、铜和金的小纳米颗粒，其特征在于一方面它们与太阳光的强相互作用（即，它们集中太阳能）并且另一方面通过它们的高化学活性（即，激活许多所需的化学转化）。这种新一代的光催化剂将补充传统上用于该领域的半导体光催化剂。Linic教授为地区高中制定的一项推广计划使当地高中生有机会参与这项研究，并了解可持续能源转型。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提供培训机会。 最近证明，当用低强度光照射时，等离子体金属纳米颗粒可以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Ag、Au和Cu）的特性使得它们与延伸的金属表面（金属块体）根本不同，该特性是它们通过局部表面等离子体共振（LSPR）的激发与UV-可见光的强共振相互作用。虽然这些初步的研究导致了一个非常活跃的等离子体金属光化学领域，但仍有许多未解决的关键问题。该项目的重点是一些这些问题，包括确定：（一）等离子体将高能电子转移到吸附物并在此过程中诱导化学转化的机制，（二）负责报告的反应速率和光强度之间的非线性依赖关系的机制，以及（三）负责观察到的等离子体金属纳米颗粒上的光化学活性位点的性质。解决这些问题对于金属纳米颗粒的光学性质、其几何结构（在单个颗粒和簇水平）及其光催化活性之间的预测关系的发展至关重要。这对于我们理解这些材料上发生的表面光化学，这些过程可以控制的程度以及影响最佳光催化系统设计的参数非常重要。

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.