The Preparation Of Graphene Supported Transition Metal Doped Platinum-based Nanomaterials And Their Electrocatalytic Properties Toward Methanol

With the shortage of fossil fuels,it is urgent to develop sustainable energy sources.As a highly efficient energy conversion device,the fuel cell plays an important role in sustainable energy utilization.Direct methanol fuel cells?DMFCs?have many advantages,such as simple design,high energy conversion efficiency,low environmental pollution,convenient fuel transportation,and easy to storage and supply,and thus become a hot research field in recent years.The catalyst plays a vital role in fuel cells.Among numerous catalysts,platinum is one of the most efficient catalysts,but it is expensive and easy to be poisoned by carbonaceous intermediate products generated during methanol electrooxidation reaction.These shortcomings greatly hinder its development and application.To overcome these shortcomings,it is of great necessity to develop bimetallic structures by combining Pt with another metal.In this dissertation,a series of transition metal-doped Pt-based nanomaterials were prepared using a simple one-step hydrothermal method.The rGO supported PtCu,PtNi and Pt Co alloy catalysts were prepared by adding the transition metal Cu,Ni,or Co as second metal into the Pt-based catalyst.The PtCu/rGO,PtNi/rGO,and PtCo/rGO nanomaterials with the specific morphology were prepared by controlling the experimental conditions such as the kind and concentration of structure-directing agents,reaction time,ratio of the metal in the precursor,reaction temperature,and concentration of GO.The morphology,structure and composition of nanomaterials were characterized by field emission scanning electron microscopy?FESEM?,high resolution projection electron microscopy?HRTEM?,X-ray diffraction?XRD?,and X-ray photoelectron spectroscopy?XPS?,etc.The electrochemical properties of the as-prepared nanomaterials were measured at a CHI 660D electrochemical workstation.The main contents are as follows:1.Using chloroplatinic acid hexahydrate and copper chloride dihydrate as metal precursors,ethylene glycol as reducing agent,and 1-decyl-3-methylimidazolium bromide([C₁₀MIm]Br)ionic liquid as structure-directing agent and capping agents.rGO supported hollow spherical PtCu nanomaterials with morphology-controllable were successfully prepared.The as-prepared PtCu/rGO nanomaterials exhibited a high electrocatalytic activity and good poisoning-resistant ability for methanol oxidation.The electrochemical active surface area of PtCu/rGO nanomaterials reached up to 71.60 m² g^-1,which was much higher than that of Pt/rGO catalysts by the same method prepared and commercial Pt/C catalysts.The hollow spherical structure increased the specific surface area of the material,thereby improving the electrocatalytic activity of the materials.2.Using chloroplatinic acid hexahydrate and nickel chloride hexahydrate as metal precursors,rGO supported urchin-like PtNi nanomaterials were prepared by one-step hydrothermal method with the assistence of choline chloride-ethylene glycol deep eutectic solvents?DES?.In this method,it is not necessary to add a reducing agent to the system,DES acts as both a structure-directing agent and reducing agent.The electrochemical test of the as-prepared PtNi/rGO modified electrode was carried out by cyclic voltammetry.The results show that the urchin-like structure increased the specific surface area of nanomaterials,making the as-prepared PtNi/r GO exhibited a good catalytic activity for methanol oxidation.3.rGO supported spherical PtCo nanomaterials were successfully prepared by using chloroplatinic acid hexahydrate and cobalt chloride hexahydrate as metal precursors,ethylene glycol as reducing agent,and L-proline as structure-directing agent by the hydrothermal method.The as-prepared PtCo nanospheres had a smooth surface and uniform size,and were uniformly dispersed on the surface of the rGO.Compared with the Pt/rGO catalysts by the same method prepared and commercial Pt/C catalysts,the as-prepared nanomaterials had a better catalytic activity and anti-toxicity,and can be used as promising catalysts toward methanol electrooxidation for fuel cells.Besides the spherical structure increased the specific surface area of the nanoparticles,rGO had good ductility can effectively increase the specific surface area of the nanomaterials,therefore improving the electrocatalytic activity of the nanomaterials.