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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. [ABSTRACT FROM AUTHOR]

A systematic study on the growth of Cr2O3 in three-dimensional cubic ordered mesoporous silica (KIT-6) and its replication through nanocasting is reported. By changing the loading time and amount of precursor, the size and shape of the obtained replica could be controlled to some extent. More interestingly, in contrast to previously published studies, when KIT-6 with an aging temperature of 100 °C, which has a high degree of interconnectivity, was used as a hard template, a cubic ordered mesoporous Cr2O3 replica with an open uncoupled subframework structure and reduced symmetry was obtained. Formation of a replica with different symmetry and uncoupled subframework structure is not only related to the degree of interconnectivity of the parent, but also strongly depends on the type of metal oxide and its growth mechanism in the silica template. Nanocasting of Cr2O3 with a low loading results in a replica with monomodal pore size distribution that has same symmetry as the hard template, whereas increasing the loading amount alters the symmetry of the replica and yields a replica with bimodal distribution. [ABSTRACT FROM AUTHOR]

A series of highly ordered mesoporous Cr2O3 were prepared through the nanocasting pathway from decomposition of chromium(Ⅵ) oxide using KIT-6 as a hard template. The effects of the calcination temperature on the crystal structure, textural parameters and magnetic properties of the material were investigated. It was found that with increasing calcination temperature, surface area and pore volume of the mesoporous Cr2O3 decreased slightly. Unpredictably, increasing calcination temperature also influences the lattice parameters of the Cr2O3 crystal, and this rearrangement in the lattice parameter leads to changes in the value of the Néel temperature. A spin-flop transition has been observed at a magnetic field smaller than that of bulk material. [ABSTRACT FROM AUTHOR]