Investigation On The Synthesis And Catalytic Properties Of Flexibility CdS Photoanode

The energy consumption is increasing with the rapid developing economic and the exhausting fossil energy.The use of the traditional fossil energy causes serious environmental pollution that threatened human life such as greenhouse effect,acid rain and so on.Solar energy,possessing the high energy value,is the promising energy source to solve the energy crisis.Unfortunately,solar energy cannot supply the steady energy due to the limitation of territory,day and night.Photoclectrochemical water splitting has been proven a very promising,environmentally friendly method to convert solar energy into chemical fuels,in which the semiconductor produces the electron/hole pairs under the light illumination.The existence of the space charge layer induces the transfer of holes between the photoanode and the electrolyte.In water splitting,the holes react with the·OH and the electrons move to the counter electrode to react with the H⁺.The band gap of photoelectrode semiconductor is better to be 1.7³.1 eV,which can absorb the 90%solar energy?400⁷00 nm?.CdS is considered to be a typical,promising visible-light absorber because of its narrow band gap,high photocurrent and superb electron mobility.However,CdS used for PEC water splitting suffered from the serious photocorrosion under the long-term illumination.The corrosion Cd²⁺is highly harmful to the water source and causes serious pollutant.The electron/hole pairs on the surface of CdS possess a high recombination rate due to the narrow bandgap.The research in this thesis is designed by following two aspects:inhibit the photocorrosion of CdS and improve the carriers'utilization efficiency.1.We have successfully synthesized a Cd S/Ni_xS_y heterostructure on Ni foam via a one-pot hydrothermal synthesis method.The heterostrure n-type CdS is surrounded by p-type Ni_xS_y with a sufficient interface to transfer excess holes quickly.P-type Ni_xS_y,the hole receiver,can replace the hole scavenger to absorb excess photogenerated holes in CdS.In LSV curves,the photocurrent of pure Cd S declined rapidly after 0.7 V.While after constructing the CdS/Ni_xS_y heterostructure,the photocurrent increased gradually up to the voltage of 1.1 V.This phenomenon clarified the improvement of the holes transfer ability between Cd S and Ni_xS_y.2.To solve the problems of instability and the high recombination rate of the carriers in Cd S,we designed and implemented a sandwich structure of porous C₃N₄/quantum dots Cd S/layer MoS₂ with facile band alignment for high photochemical performance under visible-light.The superior thermodynamics stable porous C₃N₄ supports the high specific surface area and short carriers'diffusion length.The CdS quantum dots is distributed on the surface of C₃N₄,providing a negative band gap of C₃N₄ for effective separation of electron/hole pairs.In PL spectra,the high PL peak states that the carriers recombination is also exist after the combination of CdS and C₃N₄.The conductive layer of Mo S₂ is covered on the other side of CdS quantum dots to receive the surplus carriers of C₃N₄ and CdS.This work demonstrates that fabricating appropriate ternary hybrids with the bifunction of separation/transfer is a promising strategy for developing high efficiency photocatalystst in photodegradation and photoelectrochemical.