Photoelectrochemical Evidence of Cu2O/TiO2 Nanotubes Hetero-Junctions formation and their Physicochemical Characterization

Cu2O/TiO2 nanotubes heterojunctions were fabricated by electrochemical deposition of cuprous oxide on TiO2 nanotubes arrays grown by anodizing. X-ray diffraction and Raman Spectroscopy analysis allows for identification of Cu2O, whose morphological features were studied by Scanning Electron Microscopy as a function of the charge circulated during the electrodeposition step. Photoelectrochemical measurements in aqueous solutions evidenced a red shift of the light absorption threshold of TiO2 nanotubes due to the presence of cuprous oxide even for very low circulated charges, while electrochemical impedance measurements proved a significant reduction of the electrode impedance due the presence of Cu2O. Photoelectrochemical measurements in non aqueous solutions allow to reduce reverse bias across the junction and to measure stationary cathodic photocurrent, thus confirming the formation of p-type Cu2O inside the nanotubes.