Modification of TiO2 nanotubes by Cu2O for photoelectrochemical, photocatalytic, and photovoltaic devices

The current interest in developing devices for solar powered energy conversion and storage, as well as light-induced catalytic removal of pollutants has recently prompted attention to the modification of TiO2 nanotubes with Cu2O, acting as a visible light sensitizer. This paper reviews the major challenges toward the implementation of efficient and reliable Cu2O-based devices and the efforts to overcome their drawbacks. Recent developments in the TiO2/Cu2O system for use in photovoltaics, photoelectrochemical solar cells, and photocatalysis for pollutant compound degradation are also discussed. It is shown that a plasma treatment technique improves the morphology of electrodeposited Cu2O on TiO2 nanotubes, leading to an increase in the density of photoelectrochemically active particles on the surface. We also report that under intense illumination, Cu2O on TiO2 degrades rapidly, leading to a decay in the photocurrent response; this instability severely limits the prospects of Cu2O-based photoelectrochemical devices.