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

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

The challenges for further development of Li rechargeable batteries for electric vehicles are reviewed. Most important is safety, which requires development of a nonflammable electrolyte with either a larger window between its lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) or a constituent (or additive) that can develop rapidly a solid/ electrolyte-interface (SEI) layer to prevent plating of Li on a carbon anode during a fast charge of the battery. A high Li-ion conductivity (σ Li > 10 ―4 S/cm) in the electrolyte and across the electrode/ electrolyte interface is needed for a power battery. Important also is an increase in the density of the stored energy, which is the product of the voltage and capacity of reversible Li insertion/extraction into/from the electrodes. It will be difficult to design a better anode than carbon, but carbon requires formation of an SEI layer, which involves an irreversible capacity loss. The design of a cathode composed of environmentally benign, low-cost materials that has its electrochemical potential μ C well-matched to the HOMO of the electrolyte and allows access to two Li atoms per transition-metal cation would increase the energy density, but it is a daunting challenge. Two redox couples can be accessed where the cation redox couples are "pinned" at the top of the O 2p bands, but to take advantage of this possibility, it must be realized in a framework structure that can accept more than one Li atom per transition-metal cation. Moreover, such a situation represents an intrinsic voltage limit of the cathode, and matching this limit to the HOMO of the electrolyte requires the ability to tune the intrinsic voltage limit. Finally, the chemical compatibility in the battery must allow a long service life.

Challenges for Rechargeable Li Batteries

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

The dye-sensitized solar cells (DSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. In contrast to the conventional systems where the semiconductor assume both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The use of sensitizers having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photon into electric current is achieved over a large spectral range extending from the UV to the near IR region. Overall solar (standard AM 1.5) to current conversion efficiencies (IPCE) over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. Here we present the current state of the field, discuss new concepts of the dye-sensitized nanocrystalline solar cell (DSC) including heterojunction variants and analyze the perspectives for the future development of the technology.

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Dye-sensitized Solar Cells

A study of the electrochemical growth and optical properties of polymeric thionine films on platinum using ellipsometry

The electroreduction of oxygen on thin films of platinum phthalocyanine in alkaline solutions: Part II. Spectroelectrochemical data and mechanism

Carbon electrodes have been used as cathodes in alkaline air fuel cells with some success [1-3]. The material is reasonably durable though forms that yield significant concentrations of hydrogen peroxide are slowly degraded. However, the activity of carbon can be enhanced onsiderably by impregnation with a suitable catalyst. The most ffective of these catalysts to date have proved to be noble metals uch as platinum, and 7-15 wt % platinum is commonly sed.This is a very costly route, and macrocyclic ransition-metal derivatives have also been explored as less expensive alternatives [4, 5], either as films on metallic substrates or impregnated on various forms of carbon.

High efficiency cathodes for alkaline air electrodes

The use of fractional-factorial methods in the optimization of porous-carbon electrode structure is discussed with respect to weight-loss of carbon during gas treatment, weight and mixing time of binder, compaction temperature, time and pressure, and pressure of feed gas. The experimental optimization of an air electrode in alkaline solution is described.

Andrew Hamnett

Papers

A study of the electrochemical growth and optical properties of polymeric thionine films on platinum using ellipsometry

The electroreduction of oxygen on thin films of platinum phthalocyanine in alkaline solutions: Part II. Spectroelectrochemical data and mechanism

High efficiency cathodes for alkaline air electrodes

Fractional-factorial design of a porous-carbon fuel-cell electrode

Theory of electroreflectance and photoreflectance of semiconductors