Photoelectrochemical Properties of TiO2/Sb2S3 Heterojunction with CuO Nanostructure as Photocathode

In this paper, two different nanostructures of CuO seeds layer and CuO nanocones array as photocathode were introduced for TiO2/Sb2S3 heterojunction to study the photoelectrochemical properties. The all-solid FTO/TiO2/Sb2S3/CuO seeds layer/FTO device and FTO/TiO2/Sb2S3/CuO nanocones array/FTO device could realize photoelectric conversion with a small photocurrent and photovoltage, and the photoelectrochemical properties of FTO/TiO2/Sb2S3/CuO nanocones array/FTO is even lower than that of the FTO/TiO2/Sb2S3/CuO seeds layer/FTO device due to the limited contact area between Sb2S3 and CuO nanocones. When the electrolyte I3−/I− was filled into space between Sb2S3 and CuO seeds (nanocones array) photocathode, the photoelectrochemical performance was significantly improved, especially, the photocurrent is enhanced by two (four) orders of magnitude and the photovoltage is enhanced by two orders of magnitude than the device for both photocathodes without electrolyte. For better understanding the photoelectrochemical mechanism of different CuO nanostructure photocathodes, dynamic characterization of intensity-modulated photocurrent/photovoltage spectroscopy and photoelectrochemical impedance spectroscopy were carried out to study photo-generated electron and hole behaviors. Results showed that charge transfer rate in device with CuO seeds layer photocathode is significantly enhanced by CuO nanocones array photocathode. The better hole transfer also improved the charge separation in Sb2S3 and reduced their recombination rate, which results in the enhanced photocurrent and photovoltage by CuO nanocones array photocathode.