Nanocatalysts for Solar Water Splitting and a Perspective on Hydrogen Economy.

In this review article, nanocatalysts for solar hydrogen production are the focus of discussion as they can contribute to the development of sustainable hydrogen production in order to meet future energy demands. Achieving this task is subject of scientific aspirations in the field of photo- and photoelectrocatalysis for solar water splitting where systems of single catalysts or tandem configurations are being investigated. In search of a suitable catalyst, a number of crucial parameters are laid out which need to be considered for material design, in particular for nanostructured materials that provide exceptional physical and chemical properties in comparison to their bulk counterparts. Apart from synthetic approaches for nanocatalysts, key parameters and properties of nanostructured photocatalysts such as light absorption, charge carrier generation, charge transport, separation and recombination, and other events that affect nanoscale catalysts are discussed. To provide a deeper understanding of these key parameters and properties, their contribution towards existing catalyst systems is evaluated for photo- and photoelectrocatalytic solar hydrogen evolution. Finally, an insight into hydrogen production processes is given, stressing the current development of sustainable hydrogen sources and presenting a perspective towards a hydrogen-based economy.

Development of Hydrogen Storage Tank Systems Based on Complex Metal Hydrides.

This review describes recent research in the development of tank systems based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited, especially for thermolysis-based systems where so far only demonstration projects have been performed. Hydrolysis-based systems find their way in space, naval, military and defense applications due to their compatibility with proton exchange membrane (PEM) fuel cells. Tank design, modeling, and development for thermolysis and hydrolysis systems as well as commercial applications of hydrolysis systems are described in more detail in this review. For thermolysis, mostly sodium aluminum hydride containing tanks were developed, and only a few examples with nitrides, ammonia borane and alane. For hydrolysis, sodium borohydride was the preferred material whereas ammonia borane found less popularity. Recycling of the sodium borohydride spent fuel remains an important part for their commercial viability.