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

Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Nano‐photocatalytic Materials: Possibilities and Challenges

Photochemical splitting of water into H2 and O2 using solar energy is a process of great economic and environmental interest. Since the discovery of the first water splitting system based on TiO2 and Pt in 1972 by Fujishima and Honda, over 130 inorganic materials have been discovered as catalysts for this reaction. This review discusses the known inorganic catalysts with a focus on structure–activity relationships.

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Inorganic Materials as Catalysts for Photochemical Splitting of Water

Overall water splitting to form hydrogen and oxygen over a heterogeneous photocatalyst using solar energy is a promising process for clean and recyclable hydrogen production in large-scale. In recent years, numerous attempts have been made for the development of photocatalysts that work under visible-light irradiation to efficiently utilize solar energy. This article presents recent research progress in the development of visible-light-driven photocatalysts, focusing on the refinement of non-oxide-type photocatalysts such as (oxy)nitrides and oxysulfides.

New Non-Oxide Photocatalysts Designed for Overall Water Splitting under Visible Light

The photocatalytic properties for water decomposition of RuO2-dispersed alkaline earth metal and lanthanum indates with an octahedrally coordinated In3+ ion of d10 configuration were studied. The i...

Photocatalytic Activity for Water Decomposition of Indates with Octahedrally Coordinated d10 Configuration. I. Influences of Preparation Conditions on Activity

The photocatalytic activity for water decomposition of alkaline earth metal and alkaline metal antimonates, M 2 Sb 2 O 7 (M = Ca, Sr), CaSh 2 O 6 and NaSbO 3 , was investigated. These antimonates were photocatalytically active when combined with RuO 2 : both H 2 and O 2 were produced from the initial stage of reaction under UV irradiation, and the photocatalytic activity became stable as the reaction proceeded. The photocatalytic properties are discussed based on the distorted structures of SbO 6 octahedra.

Photocatalytic water decomposition by RuO2-loaded antimonates, M2Sb2O7 (M=Ca, Sr), CaSb2O6 and NaSbO3, with d10 configuration

The photocatalytic activities for water decomposition of RuO2-loaded alkaline metal indates, AInO2 (A=Li, Na), with d10 configuration were studied. Under Hg–Xe lamp illumination, RuO2-loaded LiInO2 had little activity, but RuO2-loaded NaInO2 showed the ability to photocatalytically decompose water to hydrogen and oxygen. The photocatalytic activity strongly depended on the calcination temperature of NaInO2: with increasing calcination temperature, the activity increased, passed through a maximum, and sharply decreased. In case that a part of Na ion in NaInO2 was replaced by Li or K ion, the photocatalytic activity decreased sharply with a small amount of Li and gradually with increasing content of K. The calculation based on a plane wave density function theory (DFT) was employed to elucidate the band structure of AInO2 (A=Li, Na). The photocatalytic activities were compared with those of previously reported RuO2-loaded MIn2O4 (M=Ca, Sr), and the activity differences among them are discussed.

Photocatalytic activities for water decomposition of RuO2-loaded AInO2 (A = Li, Na) with d10 configuration

Tetragonal lead tungstate, PbWO4, consisting of a WO4 tetrahedron showed high and stable photocatalytic activity for the overall splitting of water, producing a stoichiometric quantity of H2 and O2 under UV irradiation when loading RuO2 on the metal oxide. The activity was found to strongly depend on the preparation temperature of PbWO4. In the temperature range 773−1273 K, a maximum appeared at around 1023 and 973 K when prepared in air and under a N2 atmosphere, respectively. X-ray diffraction analysis and SEM observation showed that high activity was achieved with a combination of crystallized PbWO4 with a high dispersion of RuO2 particles. The DFT calculation for PbWO4 with the d10s2-d0 electronic configuration showed that the top of the valence band (HOMO) was composed of hybridized O 2p + Pb 6s orbitals, while the bottom of the conduction band (LUMO) consisted of hybridized W 5d + O 2p + Pb 6p orbitals. Considerable dispersion was observed for both the conduction and valence bands, which differed fr...

Hiroshi Nishiyama

Papers

Photocatalytic Activity for Water Decomposition of Indates with Octahedrally Coordinated d10 Configuration. I. Influences of Preparation Conditions on Activity

Photocatalytic water decomposition by RuO2-loaded antimonates, M2Sb2O7 (M=Ca, Sr), CaSb2O6 and NaSbO3, with d10 configuration

Photocatalytic activities for water decomposition of RuO2-loaded AInO2 (A = Li, Na) with d10 configuration

Overall splitting of water by RuO2-loaded PbWO4 photocatalyst with d10s2-d0 configuration

Effects of divalent metal ion (Mg2+, Zn2+ and Be2+) doping on photocatalytic activity of ruthenium oxide-loaded gallium nitride for water splitting