The ability to systematically vary the flatband potential and the band edge positions of Cu 2 O by varying the deposition bath pH is considered important in the context of using Cu 2 O for photocatalytic water splitting. Capacitance-voltage (C-V) and dark and light current-voltage measurements were taken in order to investigate the electronic properties of electrodeposited Cu 2 O thin films grown in an acetate bath containing a 0.01 M Cupric Acetate having different bath pH values. The Mott-Schottky plots resulting from C-V measurements revealed that the flatband potential and doping density of the films strongly depended on the deposition bath pH. For pH values lower than 7.2, conductivity of Cu 2 O films remained n-type while it changed to p-type for higher pH values indicating that change of n-type to p-type character of the Cu 2 O films can be controlled by the bath pH. With increasing pH value, the grain size decreased, while crystal shapes transformed from truncated octahedral to cubic within the tested pH range. A well ordered cubic structure was observed in films deposited at pH 7.8. The rate of deposition decreased at higher pH values leading to thinner films indicating the effect of pH on the film thickness. Calculated band edge positions of conduction and valance bands of the Cu 2 O films were −4.19 eV and −6.29 eV respectively with respect to the vacuum level.

A photocatalytic composite in powder form having nanosized Cu2O/Cu granules wrapped in multilayered reduced graphene oxide (rGO) sheets was synthesized. The fabrication process was initiated by potentiostatic electrodeposition of n-type Cu2O thin films on Ti substrates in an acetate bath. Peeled-off Cu2O thin films were next subjected to ultrasonic mixing with graphene oxide (GO) by maintaining a Cu2O/GO mass ratio of 125:10. Chemical reduction using ascorbic acid converted Cu2O partially to Cu, while converting GO completely to rGO as confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Transmission electron microscopy (TEM) images of the composite confirmed the presence of Cu nanoparticles of the size of tens of nanometers within the photocatalyst, Cu2O. The fabrication process therefore implicitly favors synthesis of nanosized Cu playing the role of a co-catalyst. The Cu2O/Cu/rGO composite showed significantly higher ability to degrade methylene blue in solution, while the effects due to photocorrosion were minimal during a month of testing when compared with Cu2O alone. The layered rGO provides an effective medium for transporting photoelectrons to the reactant while inhibiting photocorrosion. Furthermore, the composite demonstrated its ability to split water under visible light in the presence of methanol and creates a promising platform to further develop a variety of other photocatalytic applications.

Electrodeposition technique is very useful for depositing n-type Cu 2 O thin films on various substrates. However, most of the reported n-type Cu 2 O thin film electrodes exhibit not only ntype photoactivity but also p-type photoactivity in photoelectrochemical cells. In this study, current-voltage characteristics and zero bias spectral response measurements were employed to investigate the possibilities to remove/minimize this unwanted p-type behaviour of n-type Cu 2 O thin films electrodeposited on Ti substrate. For this, prior deposition of Cu thin films on Ti substrate, low temperature annealing of Cu 2 O films in air and optimization of deposition bath pH were investigated. Growth of a very thin Cu film improved the n-type photosignal significantly and reduced the p-type photoresponse of the films. Films electrodeposited using an acetate bath of pH 6.1 produced only the n-type photoresponse. Low temperature annealing of Cu 2 O films in air improved the n-type photoresponse and it was found that annealing at 100 °C for 24 h produces the best result. These methods will be very useful to obtain electrodeposited Cu 2 O thin film with improved n-type photoactivity suitable for applications in thin film solar cells and other devices.