Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Optically excited plasmonic nanoparticles can activate chemical reactions on their surfaces. The underlying physical mechanisms responsible for the chemical activity and advances in photocatalysis on plasmonic metallic nanostructures are discussed. The strong interaction of electromagnetic fields with plasmonic nanomaterials offers opportunities in various technologies that take advantage of photophysical processes amplified by this light–matter interaction. Recently, it has been shown that in addition to photophysical processes, optically excited plasmonic nanoparticles can also activate chemical transformations directly on their surfaces. This potentially offers a number of opportunities in the field of selective chemical synthesis. In this Review we summarize recent progress in the field of photochemical catalysis on plasmonic metallic nanostructures. We discuss the underlying physical mechanisms responsible for the observed chemical activity, and the issues that must be better understood to see progress in the field of plasmon-mediated photocatalysis.

http://www-nature-com-443.webvpn.bjmu.tsg211.com/articles/nmat4281.pdf

Photochemical transformations on plasmonic metal nanoparticles

Visible-light-driven photochemistry has continued to attract heightened interest due to its capacity to efficiently harvest solar energy and its potential to solve the global energy crisis. Plasmonic nanostructures boast broadly tunable optical properties coupled with catalytically active surfaces that offer a unique opportunity for solar photochemistry. Resonant optical excitation of surface plasmons produces energetic hot electrons that can be collected to facilitate chemical reactions. This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasmonic metal/semiconductor heterostructures. Following that are highlights of recent examples of plasmon-driven hot electron photochemical reactions within the context of both cases. The review concludes with a discussion about the remaining challenges in the field and future oppor...

Surface-Plasmon-Driven Hot Electron Photochemistry

Plasmon-induced hot-electron transfer from metal nanostructures is a potential new paradigm for solar energy conversion; however, the reported efficiencies of devices based on this concept are often low because of the loss of hot electrons via ultrafast electron-electron scattering. We propose a pathway, called the plasmon-induced interfacial charge-transfer transition (PICTT), that enables the decay of a plasmon by directly exciting an electron from the metal to a strongly coupled acceptor. We demonstrated this concept in cadmium selenide nanorods with gold tips, in which the gold plasmon was strongly damped by cadmium selenide through interfacial electron transfer. The quantum efficiency of the PICTT process was high (>24%), independent of excitation photon energy over a ~1-electron volt range, and dependent on the excitation polarization.

http://science.sciencemag.org/content/sci/349/6248/632.full.pdf

Efficient hot-electron transfer by a plasmon-induced interfacial charge-transfer transition

Recent reports have shown that plasmonic nanostructures can be used to drive direct photocatalysis with visible photons, where nanostructures act as the light absorber and the catalytic active site. These reports have showcased direct plasmon driven photocatalysis as a route to concentrate and channel the energy of low intensity visible light into adsorbed molecules, enhancing the rates of chemical transformations, and offering pathways to control reaction selectivity. In this perspective, we will discuss the fundamental photophysics of localized surface plasmon resonance (LSPR) excitation in the context of driving chemical transformations. The various demonstrated chemical conversions executed using direct plasmonic photocatalysis will be reviewed. Experimental observations, such as the dependence of photocatalytic rate on illumination intensity and photon energy, will be related to microscopic mechanisms of photocatalysis. In addition, theoretical treatments of various mechanisms within the process of d...

Direct Photocatalysis by Plasmonic Nanostructures

Engineering heterogeneous metal catalysts for high selectivity in thermal driven reactions typically involves the synthesis of nanostructures with well-controlled geometries and compositions. However, inherent relationships between the energetics of elementary steps limit the control of catalytic selectivity through these approaches. Photon excitation of metal catalysts can induce chemical reactivity channels that cannot be accessed using thermal energy, although the potential for targeted activation of adsorbate–metal bonds is limited because the processes of photon absorption and adsorbate–metal bond photoexcitation are typically separated spatially. Here, we show that the use of sub-5-nanometer metal particles as photocatalysts enables direct photoexcitation of hybridized adsorbate–metal states as the dominant mechanism driving photochemistry. Activation of targeted adsorbate–metal bonds through direct photoexcitation of hybridized electronic states enabled selectivity control in preferential CO oxidat...

Controlling catalytic selectivity on metal nanoparticles by direct photoexcitation of adsorbate-metal bonds.

Atomic-scale insights into how supported metal nanoparticles catalyze chemical reactions are critical for the optimization of chemical conversion processes. It is well-known that different geometric configurations of surface atoms on supported metal nanoparticles have different catalytic reactivity and that the adsorption of reactive species can cause reconstruction of metal surfaces. Thus, characterizing metallic surface structures under reaction conditions at atomic scale is critical for understanding reactivity. Elucidation of such insights on high surface area oxide supported metal nanoparticles has been limited by less than atomic resolution typically achieved by environmental transmission electron microscopy (TEM) when operated under realistic conditions and a lack of correlated experimental measurements providing quantitative information about the distribution of exposed surface atoms under relevant reaction conditions. We overcome these limitations by correlating density functional theory predicti...

Quantitative and Atomic-Scale View of CO-Induced Pt Nanoparticle Surface Reconstruction at Saturation Coverage via DFT Calculations Coupled with in Situ TEM and IR

Mechanism of CO2 reduction by H2 on Ru(0 0 0 1) and general selectivity descriptors for late-transition metal catalysts

Visible light driven catalysis on metal surfaces and nanoparticles has attracted significant attention in recent years as a potential route for driving selective chemical reactions that are difficult to achieve with thermal energy. It is most often assumed that photochemistry on metal surfaces occurs through a substrate-mediated process of adsorbate-metal bond photoexcitation, although crucial underlying phenomena controlling the efficiency of this process are still poorly understood. In this work, substrate-mediated photochemistry on metal surfaces was analyzed by combining dynamical models associated with the metal substrate photoexcitation and electron-mediated bond-activation processes. An extended version of two-temperature model was utilized to treat temporal evolution of photoexcited charge carriers in the metal substrate. The electron-induced adsorbate dynamics on the metal surface was modeled using a nonadiabatic, first-principles based inelastic electron scattering model. Photoactivation of thre...

Talin Avanesian

Papers

Direct Photocatalysis by Plasmonic Nanostructures

Controlling catalytic selectivity on metal nanoparticles by direct photoexcitation of adsorbate-metal bonds.

Quantitative and Atomic-Scale View of CO-Induced Pt Nanoparticle Surface Reconstruction at Saturation Coverage via DFT Calculations Coupled with in Situ TEM and IR

Mechanism of CO2 reduction by H2 on Ru(0 0 0 1) and general selectivity descriptors for late-transition metal catalysts

Adsorbate Specificity in Hot Electron Driven Photochemistry on Catalytic Metal Surfaces