Preparation Of Heterostructures Of Cadmium Sulfide-based Nanorod Arrays And Their Photoelectric Properties

Solar-driven photoelectrochemical water splitting of semiconductor photoelectrodes is one of the potential effective ways to solve energy crisis and environmental pollution problems in the furure.Among many semiconductor materials,CdS has been considered as a promising photoanode material due to its the advantages of high electron mobility,low cost and visible light harvesting ability.In this thesis,CdS nanorod array photoanode was fabricated firstly via a facile hydrothermal method,then ?-Ni(OH)2@CdS and TiN@CdS nanorod array photoanodes were fabricated by using photodeposition and in situ oxidation method to grow ?-Ni(OH)2 nanoparticles on CdS nanorod arrays as well as via using physical adsorption to adsorb TiN nanoparticles on CdS nanorod arrays,respectively.Various characterization and testing techniques were used to characterize composition,crystalline phase,size and morphology and to study optical property and PEC performance of the prepared photoanodes.The mechanism for enhamced PEC activity was discussed and elucidated on the basis of experimental results.The thesis mainly includes the following contents:Using a simple one-step hydrothermal method,CdS nanorod arrays with hexagonal wurzite structure were sucessfully grown on fluorine-doped tin oxide(FTO)conductive glass sbustrate by using cadmium hexahydrate nitrate(Cd(NO3)2·6H2O)as the cadmium source,glutathione(g-sh)as the template as well as the sulfur source and thiourea as the sulfur source.The effect of growth temperature on the morphology of CdS nanostructures was studied.The prepared CdS nanorod arrays exhibit a strong absorption in visible light range.Under visible light irradiation,the PEC water spliitng performance CdS nanorods arrays was studied by using a three-electrode electrochemical workstation.The experimental results display that the CdS nanorods array photoanode prepared at 200? exhibits the best PEC water splitting performance.Photocurrent density of this photoanode is 1.5 and 1.1 times that of the CdS nanorods array photoanodes prepared at 150?and 180?,respectively.Using nickel hexahydrate(NiCl2·6H2O)as the nickel source,the ?-Ni(OH)2 nanoparticles were successfully deposited on the CdS nanorod arrays via a facile photodeposition and in situ oxidation method to construct ?-Ni(OH)2@CdS hetrojunction nanorod arrays.By adjusting the concentration of NiCl2 solution,the?-Ni(OH)2 nanoparticles with different deposition amounts were grown on the CdS nanorod arrays.The effect of ?-Ni(OH)2 nanoparticle loadings on the PEC water splitting activity of ?-Ni(OH)2@CdS hetrojunction nanorod arrays was studied.Under visible light irradiation at 0 V vs.Ag/AgCl,the H2 generation amount of ?-Ni(OH)2@CdS nanorod array photoanode prepared by optimizing concentration of NiCl2 solution is 8 times higher than that of pure CdS nanorod array photoanode.In addition,the prepared ?-Ni(OH)2@CdS nanorod array photoanode exhibits excellent photostability.Mott-Schottky and electrochemical spectrum measurements clearly demonstrate that synergistic action of both p-n junction and type ? band alignment integrated into ?-Ni(OH)2@CdS nanorod array photoanode fascilate the transfer and separation of photogenerated charge carriers effectively,leading to significantly improvement for PEC water splitting to produce H2.Using a simple physical adsorption method,different amounts of TiN nanoparticles were adsorbed on the surface of the CdS nanorods to fabricated TiN@CdS nanorod array structures.The effect of TiN nanoparticle loadings on the PEC water splitting activity of TiN@CdS hetrojunction nanorod arrays was studied.Under visible light irradiation at 0 V vs.Ag/AgCl,the H2 generation amount of TiN@CdS nanorod array photoanode prepared by optimizing loadings of TiN nanoparticles is 1.5 times higher than that of pure CdS nanorod array photoanode.In addition,the prepared TiN@CdS nanorod array photoanode displays the excellent photostability.The mechanism for enhanced PEC water splitting activity of TiN@CdS nanorod array photoanode was elucidated on the basis of the surface plasmon resonance(SPR)effect of TiN nanoparticles.