CdS-sensitized 1-D single-crystalline anatase TiO2 nanowire arrays for photoelectrochemical hydrogen production

We report photoelectrochemical (PEC) properties of single crystalline anatase TiO2 nanowire (NW) arrays which are sensitized with CdS for visible light activity. Photocurrent varies largely with increasing the growth time (from 2 to 24 h) of the TiO2 NWs and also increasing the deposition cycles (from 7 to 13 cycles) of CdS, which are attributed to changes in morphology of the TiO2 NWs and CdS layer. TiO2 NW array grown for 3 h with 9-cycles of CdS deposition exhibits the maximum photocurrent of 3.6 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) under the 1 SUN solar light. Morphological analysis combined with photoresponse analysis show that the 3 h-grown TiO2 NW array has the most suitable structure for PEC electrode because of large surface area for light absorption and chemical reaction, and that the 9-cycles deposited CdS layer provides the optimum light absorption and electron lifetime.