Research On Preparation Of Nanoporous Single-crystal-like Cd_xZn_1-xS Nanosheets Photocatalyst By Chemical Transformation And Its Photocatalytic And Photoelectrochemical Performance

Porous nanostructures have received considerable attention because of theirimproved chemical and physical performance over solid materials as well as theirintriguing applications in nanoreactors, actuators, energy storage, solar cells,ultrafiltration and separation, CO2capture, catalysis, cell imaging, and drug delivery.Among materials with various shapes, nanosheets have attracted intensive interests assheetlike materials may exhibit improved catalytic performance over their wirelike orspherical structures. But, the efficient synthesis of porous single-crystalline sheets stillremains a challenge. Therefore, it is of intensive interest to develop a new, simple anduniversal approach to creat porous nanosheets.Chemical transformation of nanomaterials has attracted ever-growing attentionbecause it can effectively transform material precursors into otherdifficult-direct-synthesized, complex, novel nanostructures with unique properties. Inthis thesis, we adopt the inorganic-organic hybrid ZnS-amine sheets as the startingmaterials and describe a facile cation-exchange high-yield strategy to synthesizesingle-crystal-like CdxZn1-xS nanosheets with intriguing photocatalytic andphotoelectrochemical performance.The main results are listed as follows:1. We report a cation-exchange strategy to synthesize nanoporoussingle-crystal-like CdxZn1-xS nanosheets and their photocatalytic performance. Weadopt the inorganic-organic hybrid ZnS–DETA sheets as the starting materials anddescribe a facile cation-exchange strategy to fabricate single-crystal-like porousnanosheets. The pore size and composition of the nanoporous products can bemodulated by changing the solvent and varying the ration of the hybrid precursor andcation ions, respectively. The nanoporous single-crystal-like CdxZn1-xS nanosheetswere characterized by SEM, TEM, XRD etc. The photocatalytic H2production of theresulting nanoporous single-crystal-like Cd0.5Zn0.5S nanosheets was systematicallyexplored under visible light. It was found that we report the synthesis of nanoporoussinglecrystal-like CdxZn1-xS nanosheets with good structural stability bycation-exchange reactions of the prepared ZnS–DETA hybrid nanosheets with Cd2+cations. The pore size and composition of the nanoporous CdxZn1-xS sheets aremodulated by changing the solvent and varying the ratio of the hybrid precursor to cadmium ions, respectively. The porous Cd0.5Zn0.5S nanosheets show a highercatalytic performance relative to their solid crystals for the photocatalytic H2evolution from water splitting.2. The fabrication of stable nanoporous Zn0.5Cd0.5S nanosheets/reduced grapheneoxide (Zn0.5Cd0.5S/RGO) photoelectrode via a facile in-situ photoreduction methodand its photoelectrochemical activities. Graphene oxide (GO) and nanoporousZn0.5Cd0.5S nanosheets were dissolved in the solution and followed by ultrasonictreatment to make a slurry. For a working electrode fabrication, the suspension wasspreading onto transparent Indium tin oxide (ITO) glass substrate, and then dried in avacuum oven to obtain a thin film electrode, following by immersed into the sacrificeagent. After irradiation for several minutes, the color of the thin film gradually turnedfrom yellowish to dark-yellow, indicating the photoreduction of GO to RGO.Compared to pristine Zn0.5Cd0.5S photoelectrode, the as-prepared Zn0.5Cd0.5S/RGOphotoelectrode exhibits the excellent stability and enhanced photoelectrodechemicalactivities. This improvement may be ascribed to the excellent absorption, optimalelectrical conductivity, and remarkable electron storage and shuttling of RGO.Furthermore, this strategy presented here would be extended to develop other stablephotoelectrode.