Preparation Of Platinum-based Core-shell Nanocomposites Based On Graphene Quantum Dots And Its Electrochemical Catalysis Of Methanol

Direct methanol fuel cell（DMFC）have become hotspots in new energy research due to their high energy conversion efficiency,low pollution,and wide fuel sources.A large number of studies have shown that anode catalyst is one of the bottlenecks restricting further improvement of DMFC energy conversion efficiency and large-scale commercial development.Therefore,finding low cost,high activity and high stability electrocatalysts has always been a research focus in the field of DMFC.Based on graphene quantum dots（GQDs）,a new type of carbon nanomaterial that has appeared in recent years,two Pt-based metal nanocomposites with core-shell structures have been synthesized and used as anodes.The catalyst studied the electrochemical oxidation of methanol.The results show that due to the rich functional groups on the surface of GQDs（such as:-COOH,-CHO,etc.）and their unique physical and chemical properties,they can effectively disperse metal nanoparticles,increase the catalytic activity surface of the catalyst,and improve the utilization of Pt metal.Compared with the commercial catalyst Pt/C,the two core-shell Pt-based catalysts synthesized in this paper have greatly improved their catalytic activity,stability,and anti-poisoning performance.The specific research content is as follows:1.The Au-GQDs@Pt Core-shell nanocomposite was synthesized by a two-step reduction method using Au nanoparticles as core,GQDs as intermediate layer and Pt nanoparticles as shell.Through transmission electron microscopy（TEM）,energy dispersive X-ray（EDX）and X-ray photoelectron spectroscopy（XPS）,the material was characterized and found that GQDs can be assembled with Pt nanoparticles throughπ-π*conjugate bonds to form dendritic Pt.Meanwile,the thickness of Pt shell can be easily adjusted by changing the concentration of PtCl₆^2-.In alkaline media,the electrocatalytic activity of Au-GQDs@Pt for methanol oxidation is 2.5 times that of commercial Pt/C,and its anti-CO poisoning performance is also greatly improved.2.On the basis of the above work,the Au-GQDs@Ag Core-shell nanocomposite was first prepared by chemical reduction method,and then the galvanic replacement reaction between PtCl₆^2-and Ag was used to obtain Au-GQDs@AgPt Yolk-shell nanocomposite.The electrocatalytic performance of methanol on alkaline media was studied.The research results show that this material shows excellent catalytic activity(catalytic current 33.20mA cm^-2,about 7 times of commercial Pt/C),and the CO resistance and stability have been further improved.