Can point defects work to your advantage? New insights into TiO2@n-type Cu2O heterostructures

Heterostructures of TiO 2 @n-type Cu 2 O are prepared using a simple and inexpensive method of electrochemical growth of copper(I) oxide on titanium foil in an alkaline environment. Structural analysis (Raman spectroscopy) reveals the presence of defective Cu 2 O and a layer of TiO 2 (anatase and rutile) on the surface of Ti. SEM analysis indicates that increasing the deposition time leads to the formation of complex multilayer Cu 2 O structures, whereas increasing the pH from 9 to 12 results in the formation of compact layers of pyramidal Cu 2 O crystals. Current measurements in a photoelectrochemical cell (PEC) under light switching conditions imply that Ti/ TiO 2 @Cu 2 O heterostructures exhibit photoactivity that increases with electrodeposition time. Kelvin probe measurements demonstrate that increasing the Cu 2 O deposition time results in a rise in the contact potential difference (CPD), which is attributed to the quantity and uniformity of the deposited oxide. XPS analysis of the Cu 2p₃/₂ and Cu LMM spectra confirms that the dominant oxidation state in the deposited layers is Cu⁺, characteristic of Cu 2 O, and analysis of the O 1 s spectrum indicates the presence of oxygen vacancies. Importantly, analysis of the PEC, Kelvin probe, and Mott-Schottky results unanimously confirms the n-type conductivity of Cu 2 O. Based on the measurements, a mechanism for carrier charge transfer between heterostructure elements is proposed.