In this article, we report the results of comparative studies of photoelectrochemical behavior of the binary CdS/TiO2 and WO3/TiO2 and ternary CdS/WO3/TiO2 heterostructures based on titania nanotube and planar structures. Physical–chemical characterization by XRD, XPS, and electron microscopy methods together with electrochemical impedance spectroscopy measurements confirm a successful formation of heterostructured electrodes, both nanotube-based and planar. The results of photoelectrochemical studies of the heterostructures demonstrate a significant difference in their behavior depending on the structure geometry and the character of the formed heterojunctions. It is concluded that nanotube-based heterostructure electrodes can be characterized by a stochastic set of different heterojunctions while planar systems demonstrate well-ordered heterojunctions with a strictly defined electron transfer direction. Particularly, we demonstrate the possibility of the realization of Z-scheme of photoexcitation and charge separation in ternary planar systems under visible light irradiation.

The crystal structure of the Ba1.264(4)Bi1.971(4)O4 perovskite-like system and associated electronic band structure and density of states.

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