These theoretical studies presented the
Artificial photosynthesis represents the photoelectrochemical (PEC) splitting of water into hydrogen and oxygen with the help of solar light and appropriate photocatalyst  and . The vision of efficient and low cost water splitting CD 1530 is still far from an economically viable solution, mainly due to the non-availability of semiconductor materials, possessing high PEC activity and chemical stability under harsh conditions  and . To improve the PEC properties of existing metal oxide semiconductors different approaches have been adopted as documented in a large number of publications , , ,  and . Among various n-type metal oxides, TiO2 and Fe2O3 have attracted substantial attention due to their low cost, high abundance and stability under oxidative conditions  and . In this context, another promising material is WO3, which was comparatively less favored due to the fact that the conduction band of WO3 is not sufficiently negative to cause the reduction of hydrogen without an external bias voltage . Augustynski et al. and others have shown that nanostructuring of WO3 anodes can optimize the electron transport pathways and electrode–electrolyte interface, which effectively extends the electrochemical activity and light-harvesting properties  and . The preparation of WO3 films by different techniques such as sol–gel, CVD, PVD and anodization (Table 1) have shown that water-splitting properties of WO3 photoanodes is largely influenced by morphology, microstructure and phase composition as well as contact area between the film and charge collector.