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项目资助的项目中，密歇根大学（安娜堡）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由银、铜和金组成的小纳米颗粒，它们的特点一方面是与太阳光的强烈相互作用（即，它们能集中太阳能），另一方面是它们的高化学活性（即，激活许多所需的化学转化）。这一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教授为地区高中开发的外展计划使当地高中学生有机会参与这项研究并了解可持续能源转型。这项工作更广泛的影响包括发现新一代光催化剂带来的潜在社会效益，以及为学生和教师提供培训机会。最近的研究表明，当低强度光照射时，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（Ag， Au和Cu）的特性使它们与延伸的金属表面（金属体）根本不同，它们通过局部表面等离子体共振（LSPR）的激发与紫外-可见光发生强烈的共振相互作用。虽然这些初步的研究导致了等离子体金属光化学领域的一个非常活跃的领域，但仍有许多悬而未决的关键问题。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剂并在此过程中诱导化学转化的机制；(2)反应速率和光强度之间非线性依赖的机制；(3)在等离子体金属纳米颗粒上观察到光化学的活性位点的性质。解决这些问题对于发展金属纳米粒子的光学性质、几何结构（在单粒子和簇水平）和光催化活性之间的预测关系至关重要。这对于我们理解发生在这些材料上的表面光化学，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.