Controllable preparation and efficient visible-light-driven photocatalytic removal of Cr(VI) using optimized Cd_0.5Zn_0.5S nanoparticles decorated H-Titanate nanotubes

Based on one-dimensional (1D) H-titanate nanotubes (H-TNTs: TNTs with loosely distributed H⁺ across the interlayers), a novel series of Cd_0.5Zn_0.5S loaded H-TNTs (Cd_0.5Zn_0.5S/TNTs) composites with varied ratios have been achieved by the in-situ growth method. The as-prepared samples were characterized by (high-resolution) transmission electron microscopy (HR/TEM), XRD, FT-IR, XPS, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), fluorescence spectroscopy (FL), photocurrent, electron spin resonance (ESR) spectroscopy, etc. These studies concurrently revealed a successful formation of Cd_0.5Zn_0.5S/TNTs heterojunction, and a homogeneous distribution of Cd_0.5Zn_0.5S nanoparticles over the surface of 1D H-TNTs. The incorporation of the appropriate amount of Cd_0.5Zn_0.5S nanoparticles (10%) significantly improves the efficiency of photogenerated electron-hole pairs separation. The photocatalytic reduction efficiency of the Cd_0.5Zn_0.5S/TNTs for Cr(VI) and degradation efficiency for organic molecules increased initially and then decreased with the amount of loaded Cd_0.5Zn_0.5S nanoparticles. The optimal photocatalytic efficiency was observed at 10 %Cd_0.5Zn_0.5S/TNTs, which were 2.71-fold and 4.8-fold than that of pure H-TNTs for the removal of the Cr(VI) and the degradation of the organic molecules, respectively. The ESR test signified that the holes (h⁺) and superoxide radicals (∙O₂^–) played an essential role in the degradation process of organic molecules. Finally, a reasonable explanation for enhanced photocatalysis performance was proposed.