Polymer-assisted Deposition Derived Molybdenum Disulfide Nanomaterials For Optoelectronics And Electrocatalysis

MoS₂ is transition metal dichalcogenides?TMD?material,have attracted considerable attention for their great potential in the fields of catalysis,nanotribology,microelectronics,lithium batteries,hydrogen storage,medical and optoelectronics.MoS₂ has a thickness-dependent bandgap changing from 1.9 eV for single-layer MoS₂?direct bandgap?to 1.3 eV for bulk MoS2?indirect band gap?.In fact,the Eg change of MoS2 with thickness has previously been forecasted by theoretical estimations,this characteristic make MoS₂ film has huge potential in phototransistor devices.In addition,MoS₂-based electrocatalysts have been considered as promising alternatives for platinum due to their high abundance and low cost.Because MoS₂ is prone to form two-dimensional?2D?morphology that offers large surface area and 2D permeable channels for ion adsorption and transport,and MoS₂ is earth-abundant composition,which make MoS₂ become effective HER electrocatalysts that replace noble metal such as Pt.Here in,we first report an aqueous solution approach,polymer-assisted deposition?PAD?,to grow the thickness-controlled MoS₂ nanofilms and ultrathin MoS₂ nanosheets,which were applied to the optoelectronics and electrocatalytic hydrogen evolution reaction?HER?,respectively.The main subjects of this thesis are concluded as follows:1.We grow thickness-controlled MoS2 films on Si/SiO2 substrate.Firstly,the polyethyleneimine?PEI?and ethylene-diamine-tetra acetic acid?EDTA?were used to bind the molybdenum ions to form the aqueous homogeneous polymeric precursor;then the Mo precursor solution was spin-coated onto the Si/SiO₂ substrate;Finally,the precursor films are annealed in an Ar/H₂ gas to grow thickness-controlled MoS₂ film.Through many experiments,we find that there is a nearly linear relationship between the MoS₂ films thickness and the concentration of Mo precursor,which indicating the MoS₂ thickness is well controllable.Because the thickness-dependent bandgap adjustment,MoS₂ nanofilm were applied in electronic and optoelectronic devices.2.Through controlling the suitable annealing temperature,we achieved a large scale of self-supported vertical MoS₂ ultrathin nanosheets directly sulfurized and decomposition of PEI and Mo ions of precursor.The thickness of the MoS2 nanosheets is in the range of 1⁴nm?1⁷ layers?and and the average size of nanosheets is smaller than 30 nm.Ultrathin and ultrasmall nanosheets mean large BET surface area and abundant active edge sites,which demonstrated high electrochemical activity performance in the HER.