Photoelectrochemical applications of semiconducting metal oxides are continuously growing and gaining a considerable interest in view of enhanced production of renewable energy. However, overcoming intrinsic limitations of well-known and recognized towards specific action semiconducting oxides such as iron oxide, titanium oxide, tungsten oxide or copper oxide requires development of new nanoarchitectures. Given the band edges positions are not always suitable for a desired solar driven process, of primary importance is to enhance the intrinsic properties of the building materials and couple them with a catalytic modification of the surface. Therefore, efforts including development of new hetero-nanostructures and their implementation to the different type of junctions employed in solar arrangements, are continuously devoted to minimization of the required bias voltage, improvement of light capture or charge separation and collection. Recently, these approaches allowed to develop a highly active catalytic system consisting of a mesoporous semiconducting metal oxide (tungsten trioxide, titanium dioxide or iron oxide) and attached thereto polyoxometalate based WOC. The stable and reproducible water splitting photocurrents reached 4.5 mA cm^-2 for WO₃ based working system and were attained at standard conditions. In this scenario, incorporated in small amount polyoxometalates act as highly effective molecular OER catalysts leading to very large enhancement of water oxidation photocurrents [1]. These findings have also been transferred to other semiconducting systems relying onto engineered low sub-stoichiometric disorder in TiO₂ or hexagonal WO₃ conjugated to copper (I) oxide, enhanced and stabilized by the presence of heterojunction [2]. A special attention will be paid to their stabilization, intentional modification, as well as optimization of experimental conditions, permitting control and diversification of the reaction products.

[1] M. Sarnowska, K. Bienkowski, P. J. Barczuk, R. Solarska, J. Augustynski, Adv. Energy Mater. (2016), 1600526

[2] E. Szaniawska, K. Bienkowski, I. Rutkowska, P. Kulesza, R. Solarska, Cat. Today (2017) doi.org/10.1016/j.cattod.2017.05.099