Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H-2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

Single-atom catalysis of CO oxidation using Pt1/FeOx

Photoinduced reactivity of titanium dioxide

Mg-Al mixed oxides as highly active acid-base catalysts for cycloaddition of carbon dioxide to epoxides

Hydrogen, a clean energy carrier, should be produced from not the irreproducible fossil fuels but renewable resources. Currently hydrogen is mainly produced by the reforming of petroleum and natural gas at high temperature, which consumes huge energy. Thus, development of an alternative hydrogen production method is absolutely imperative to mitigate the environmental and energy issues. Photocatalytic hydrogen production from water and renewable resources is one of the attractive systems, since it can utilize the solar energy. In this short review, we remind you that the systems of the photocatalytic hydrogen production from water and biomass derivatives, such as ethanol, glycerol, sugars and methane, should be considered as available candidates for the hydrogen production method from renewable resources and solar energy, and these systems have been improved by developments of new photocatalysts with some cocatalysts, modifications of photocatalysts, optimization of reaction conditions, and so on.

Heterogeneous photocatalytic hydrogen production from water and biomass derivatives

Silver-alumina catalysts prepared by sol–gel method (Ag-Al2O3) and impregnation method (Ag/Al2O3) were studied for the selective catalytic reduction (SCR) of NO by higher alkanes (n-hexane and n-octane). UV–VIS and Ag K-edge XAFS results established the structure of the catalysts; below 2 wt.%, highly dispersed Ag+ ions are predominant Ag species, while at higher Ag loading, Agn clusters are predominant. A relationship between the structure of Ag species and their catalytic function for SCR by n-octane was clarified. Ag+ ions are responsible for the selective reduction of NO to N2, while the Agn clusters are responsible for the hydrocarbon combustion and N2O formation. The mechanism of SCR by n-hexane on Ag-Al2O3, which mainly consists of Ag+ ions, were investigated by in situ FTIR spectroscopy. During NO+n-hexane+O2 reaction, the acetate produced via the partial oxidation of n-hexane and the nitrates produced via the oxidation of NO were main adspecies in the steady-state condition at 473–623 K. The acetate, which was stable in O2 or NO, was reactive in NO+O2. Nitrates, which were relatively stable in n-hexane, were quite reactive toward n-hexane+O2. The rate of nitrates reaction in n-hexane+O2 was close to the steady-state rate of NO reduction over wide range of temperature, indicating that the nitrate is a possible intermediate in the SCR. A proposed mechanism, suggesting the reaction of nitrates with partially oxidized hydrocarbon species as a crucial step, explains the steady-state kinetic results. At relatively high NO concentration or at low temperature, nitrates should inhibit the reaction by strongly adsorbing on the catalyst surface.

Silver-alumina catalysts for selective reduction of NO by higher hydrocarbons: structure of active sites and reaction mechanism

Various efforts have been carried out to convert methane to more useful chemicals and hydrogen. However, due to its high stability, high energy is usually consumed for its conversion, which still remains as a problem to be solved. Recently, photocatalysis has been proposed to be one of the answers to break the thermodynamic barrier. This tutorial review provides a brief history about developments in the methane conversion and specially highlights the developments in the photocatalytic conversion of methane, such as methane coupling and methane conversion with other molecules.

Photocatalytic conversion of methane

Subnanometer Pd clusters stabilized within micelles of random copolymers were formed by direct immobilization of Pd(0) via ligand exchange. The clusters were estimated to contain approximately seven Pd atoms on average (cluster diameter ≈ 0.7 nm). Several Pd-containing micelle morphologies could be obtained by polymer cross-linking. These micelles containing Pd clusters were demonstrated to be efficient catalysts for hydrogenations and Heck reactions.

Hisao Yoshida

Papers

Mg-Al mixed oxides as highly active acid-base catalysts for cycloaddition of carbon dioxide to epoxides

Heterogeneous photocatalytic hydrogen production from water and biomass derivatives

Silver-alumina catalysts for selective reduction of NO by higher hydrocarbons: structure of active sites and reaction mechanism

Photocatalytic conversion of methane

Formation of nanoarchitectures including subnanometer palladium clusters and their use as highly active catalysts.