Respective construction of Type-II and direct Z-scheme heterostructure by selectively depositing CdS on {001} and {101} facets of TiO2 nanosheet with CDots modification: A comprehensive comparison

Directional deposition has always been a focus issue in the construction of specific heterostructure. Herein, for the first time, we have demonstrated that the CdS could be selectively deposited on {001} or {101} facets of TiO2 nanosheet, and two different charge transfer processes were formed. First, the selective deposition of CdS on {001} facets of TiO2 nanosheet ({001}TiO2/CdS) would form the Type-II heterostructure, which seriously weakened the redox ability of {001}TiO2/CdS and directly resulted in the low photocatalytic performance (4-Chlorophenol (4-CP), 61.92% in 40 min) and serious photocorrosion of CdS. In contrary, the selective deposition of CdS on {101} facets of TiO2 nanosheet ({101}TiO2/CdS) could construct direct Z-scheme heterostructure with significantly increased photocatalytic 4-CP degradation efficiency (96.12%), much higher than pristine TiO2 nanosheet (87.21%). The hybrids were further modified by carbon nanodots (CDots) ({101}TiO2/CdS/CDots) to enhance photocatalytic performance (99.84%). The obtained direct Z-scheme {101}TiO2/CdS/CDots showed excellent stability and anti-photocorrosion ability. The synergistic effect between TiO2 nanosheet, CdS and CDots was expounded through characterization analyses, and the photocatalytic reaction mechanism was proposed in detail. Toxicity assessment authenticated good biocompatibility and low cytotoxicity of {101}TiO2/CdS/CDots. Our discovery was expected to drive great advances in the use of TiO2 nanosheet for environmental remediation.