This article summarizes the photocatalytic water splitting performance improvement with a heterojunction system.

This review focuses on tungsten oxide (WO3) and its nanocomposites as photoactive nanomaterials for photoelectrochemical cell (PEC) applications since it possesses exceptional properties such as photostability, high electron mobility (~12 cm2 V−1 s−1) and a long hole-diffusion length (~150 nm). Although WO3 has demonstrated oxygen-evolution capability in PEC, further increase of its PEC efficiency is limited by high recombination rate of photogenerated electron/hole carriers and slow charge transfer at the liquid–solid interface. To further increase the PEC efficiency of the WO3 photocatalyst, designing WO3 nanocomposites via surface–interface engineering and doping would be a great strategy to enhance the PEC performance via improving charge separation. This review starts with the basic principle of water-splitting and physical chemistry properties of WO3, that extends to various strategies to produce binary/ternary nanocomposites for PEC, particulate photocatalysts, Z-schemes and tandem-cell applications. The effect of PEC crystalline structure and nanomorphologies on efficiency are included. For both binary and ternary WO3 nanocomposite systems, the PEC performance under different conditions—including synthesis approaches, various electrolytes, morphologies and applied bias—are summarized. At the end of the review, a conclusion and outlook section concluded the WO3 photocatalyst-based system with an overview of WO3 and their nanocomposites for photocatalytic applications and provided the readers with potential research directions.

The layer-by-layer (LbL) technique is one of the most promising ways of fabricating multilayer thin films and coatings with precisely controlled composition, thickness, and architecture on a nanometer scale. This chapter considers the multilayer thin films and coatings containing metal nanoparticles. The main attention was paid to LbL films containing metal nanoparticles assembled by convenient methods based on the different intermolecular interactions, such as hydrogen bonding, charge transfer interaction, molecular recognition, coordination interactions, as driving force for the multilayer buildup. Much attention has paid to the LbL films containing metal nanocomposites for multifunctional catalytic applications, in particular, photocatalysis, thermal catalysis, and electrocatalysis. The preparation protocol of LbL-assembled multilayer thin films containing metal nanoparticles (such as Au, Ag, Pd, Pt), metal oxides (Fe 3 O 4 ), and sulfides (CdS) that are supported on the various surfaces of nanotubes of TiO 2 , Al 2 O 3 membranes, graphene nanosheets, graphene oxide and further applications as catalysts with respect to photocatalytic, electrocatalytic performances is discussed. The systematization and analysis of literature data on synthesis, characterization, and application of multilayer thin films and coatings containing metal nanoparticles on the diverse supports may open new directions and perspectives in this unique and exciting subject.

This study focuses on understanding the fundamentals of energy transfer and electron transport in photovoltaic devices with uniquely designed nanostructures by analysing energy transfer in purple photosynthetic bacteria using dye-sensitised solar cell systems. F€ orster resonance energy transfer between the xanthene dye (donor of energy) and a new polymethine dye (acceptor of energy) was studied in dye-sensitised solar cells, which leads to a doubling of energy conversion efficiency in comparison to the cell with only the polymethine dye. The electron transport in the two different nanostructures of zinc oxide (nanorods and nanosheets) was investigated by spectroscopic methods (UV-vis spectrometer, time-resolved photoluminescence spectroscopy) and electrochemical potentiostat methods. The nanosheet structure of zinc oxide showed high short circuit current and long diffusion length. This fundamental study will lead to efficient artificial photosystem designs.