Graphene-Templated Bottom-up Fabrication of Ultralarge Binary CdS-TiO2 Nanosheets for Photocatalytic Selective Reduction

A bottom-up strategy based on graphene (GR) template is developed to synthesize free-standing TiO2 nanosheets. A cross-link of GR nanosheets and a homogeneous coating of TiO2 onto the self-assembled GR surfaces are simultaneously achieved by functionalizing the GR surface with benzyl alcohol. Followed by thermal treatment in air, the 2D TiO2 structure with ultralarge lateral size far beyond the size of original GR nanosheets (several hundred nanometers) has been built with GR as a sacrificial template. The resultant TiO2 nanosheets (TiO2-NS) are then homogeneously photodeposited with CdS nanocrystals, and thus the CdS-TiO2 composite nanosheets (CdS-TiO2-NS) are obtained. Using simulated solar light as energy source, the CdS-TiO2NS exhibits much higher activity than that of bare TiO2NS toward selective gas-phase reduction of CO2 and liquid-phase reduction of nitroaromatics. The improved photocatalytic activities of CdS-TiO2-NS benefits from (1) the deposition of narrow-band gap CdS can effectively extend the light absorption range of wide-band gap TiO2NS and (2) the unique 2D structure of TiO2-NS provides abundant coupling interface for CdS decoration, which is beneficial for photogenerated charge-carrier transport across the interfacial domain. It is hoped that our work will promote further interest in the fabrication of new 2D materials using functional GR as a sacrificial template for diverse photoredox applications.