Single CuO x thin films and n-p type bilayers of TiO 2 /CuO have been grown by rf magnetron sputtering under well-controlled content of oxygen in the reactive Ar + O 2 mixture (from 10% to 40%) and with intentionally varied thickness of the top TiO 2 layer (from 27 to 150 nm). Their morphology, structural, optical, electronic properties have been studied by SEM, TEM, XRD, XRR, UV-VIS-NIR spectrophotometry, and XAS, respectively. Photocurrent kinetics under UV light indicate that TiO 2 /CuO bilayers similarly to CuO single layers behave as photocathodes in the process of green hydrogen generation. NO 2 gas sensing at very low concentration of 50 ppb is possible at room temperature but the enhanced response of 14.5% at 1 ppm is reached for TiO 2 (52 nm)/CuO bilayer upon UV illumination. The mechanism of interaction with light is proposed and includes analysis of Mott-Schottky plot to determine band alignment after contact for TiO 2 and CuO. Double role of TiO 2 /CuO bilayers as photoelectrodes in water photolysis and gas sensors is attributed to the photocatalytic processes taking place at the surface of the top TiO 2 component of the heterostructure. • TiO 2 /CuO thin film obtained by rf magnetron sputtering form a heterojunction. • TiO 2 /CuO bilayer could be used both as phototelectrode in the water splitting process and for NO 2 gas sensing. • Different thickness of top TiO 2 film influence the photocurrent and sensor response.
Banaś et al. (2026) studied this question.