Preparation of CdS NCs decorated TiO2 nano-tubes arrays photoelectrode and its enhanced photoelectrocatalytic performance and mechanism

CdS nano-crystallites decorated TiO2 nano-tubes arrays (CdS NCs/TiO2 NTAs) photoelectrodes were prepared through anodization, followed by electrodeposition strategy. Subsequently, structures of the resulting CdS NCs/TiO2 NTAs samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, the light absorption capacities and photoelectrochemical (PECH) properties were investigated through UV-visible diffuse reflectance spectrum (DRS), photocurrent response (PCR) and open-circuit photovoltage (OCP). Furthermore, photodecomposition performances were evaluated by the yield of OH radicals and photoelectrocatalytic (PEC) degradation of rhodamine B (RhB) under Xenon light irradiation. Moreover, the enhanced PC mechanism was proposed and confirmed through photoluminescence (PL) spectra and contribution of different reactive species. Results showed that hexagonal CdS NCs with uniform spherical sizes of 20 nm were successfully deposited onto the surface of highly ordered TiO2 NTAs, which could not only red-shift the light absorption to visible region between 400 and 700 nm, but also significantly enhance the generation of OH radicals. Furthermore, CdS NCs/TiO2 NTAs photoelectrodes possessed higher transient photogenerated current of 9.62 mA cm−2 and open-circuit photovoltage of −0.253 V cm−2 than that of bare TiO2 NTAs. Moreover, when external potential (−2 V) was applied, CdS NCs/TiO2 TNTAs samples performed higher PEC efficiency of 91.6%, which could be attributed to the intense light harvesting in visible region and high mobility and separation efficiency of photogenerated charge carriers.