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

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

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.

Ordered mesoporous materials in catalysis

Measurement of the acidity of various zeolites by temperature-programmed desorption of ammonia

The effect of H2 on the selective reduction of NO by light hydrocarbons over Ag/Al2O3 catalyst under lean-exhaust conditions was investigated. The NO reduction activity at the low temperature region was markedly increased by adding H2. The NO reduction activity at high GHSV condition and SO2 tolerance were also improved by adding H2. Since the NO was reduced little by H2 in the absence of C3H8, H2 should act as a promoter of NO reduction by hydrocarbons over Ag/Al2O3. The results of reaction studies and in situ IR experiments showed that the possible reasons for promoting the effect by H2 on the HC-SCR were mainly caused by the activation of hydrocarbons.

Promotion effect of H2 on the low temperature activity of the selective reduction of NO by light hydrocarbons over Ag/Al2O3

Silver–aluminum mixed oxide catalyst (Ag–Al2O3) prepared by the sol–gel method was studied for the selective reduction of NO by various alkanes in the presence of water vapor. As the carbon number of alkanes increases, the de-NOx activity and water tolerance were markedly increased. In the case of n-octane as a reductant, the presence of water vapor markedly promoted NO reduction. The results of reaction studies and in situ IR experiment showed that the possible reasons for the promoting effect by water vapor are the inhibition of the n-octane oxidation by O2 and the suppression of the poisoning effect caused by carboxylate and carbonate species. Among various alumina-supported transition metal catalysts, Ag–Al2O3 showed the highest activity for SCR by n-octane. Ag–Al2O3 showed higher NO conversion to N2 and selectivity than alumina-supported Pt and Cu-ZSM-5 catalysts for the selective reduction of NO by n-octane and i-octane.

Catalytic performance of Ag-Al2O3 catalyst for the selective catalytic reduction of NO by higher hydrocarbons

Systematic X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (AES), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies were undertaken to investigate the electronic structure, chemical states and local geometry of the active species in the CuO/ZnO/Al2O3/ZrO2 multicomponent mixed oxide catalysts employed in the oxidative steam reforming of methanol (OSRM) reaction for H2 production. The core level XPS and AES indicated the existence of CuO and ZnO-like species. Two kinds of zirconium species, one similar to that of ZrO2 and another with relatively higher electron density were noticed from the Zr 3d core level XPS of Zr- containing catalysts. The valence band (VB) XPS studies revealed that for Zr-containing catalysts, the Cu 3d anti-bonding orbital splits from the main
VB and shifts toward lower binding energy (BE). The surface Cu/(Al + Zr) ratios were found to be close to those in the bulk while segregation of Zn at the surface was evidenced in all samples. The XANES and EXAFS results also indicated the existence of CuO and ZnO-like species, whose local environments are modified with respect to the chemical composition. The EXAFS study of the Zr-containing catalysts indicated the existence of a “Cu–O–Zr” bonding with a Cu–Zr distance in the range 3.5 to 3.9 A. The results indicated the existence of a Cu–Zr synergistic interaction in these catalysts which improved the catalytic performance in the OSRM reaction

/pdf/xps-xanes-and-exafs-investigations-of-cuo-zno-al2o3-zro2-hbpzceie64.pdf

Tadashi Hattori

Papers

Measurement of the acidity of various zeolites by temperature-programmed desorption of ammonia

Promotion effect of H2 on the low temperature activity of the selective reduction of NO by light hydrocarbons over Ag/Al2O3

Catalytic performance of Ag-Al2O3 catalyst for the selective catalytic reduction of NO by higher hydrocarbons

XPS, XANES and EXAFS investigations of CuO/ZnO/Al2O3/ZrO2 mixed oxide catalysts

Fine control of the pore-opening size of zeolite ZSM-5 by chemical vapor deposition of silicon methoxide