One-pot Strategy For Controllable Synthesis Of Reduced Graphene Oxide Supported Platinum-based Core-shell Nanocomposites And Their Electrocatalysis Research

Fuel cells are a kind of power generation device,which can directly convert chemical energy into electrical energy via the electrochemical method.The advantages of fuel cells,such as,high efficiency,environmental friendly and low noise,make them be one of the most promising energy conversion technologies.The catalyst is the key material in fuel cells,which has great influence on the cost,performance and life of fuel cells.Currently,Pt-based nanomaterials have been widely used as catalysts for anode and cathode reactions in fuel cells.However,the soaring price and scarce abundance of Pt have become the biggest impediments to the commercialization of fuel cells.The core-shell structure catalyst has become a research hotspot in the field of fuel cells due to its outstanding properties in reducing the loading of platinum and improving the catalytic activity of the catalyst.Meanwhile,the catalyst support is also of great importance in improving the catalytic activity and stability.In this study,we fabricated four reduced graphene oxide supported Pt-based core-shell nanocomposites by a simple one-pot method.The morphology,structure and composition of these obtained nanomaterials were characterized by a series of characterization techniques,and their formation mechanism was investigated in some detail.Besides,we also studied the catalytic activity and stability of these prepared nanomaterials.Specific research contents are as follows:(1)One-pot seedless aqueous synthesis of reduced graphene oxide supported core-shell Pt@Pd nanoflowers as advanced catalysts for oxygen reduction and hydrogen evolutionHerein,reduced graphene oxide supported core-shell Pt@Pd nanoflowers(Pt@Pd NFs/rGO)were fabricated by a single-step,seedless wet-chemical approach at room temperature,only using 3-aminopyrrolidine dihydrochloride(APDC)as the weak stabilizer and structure-director.The morphology,structure and composition of the product were characterized by a series of characterization techniques,and the formation mechanism was discussed in details.The nanocomposite exhibited improved catalytic activity for oxygen reduction reaction with the positive onset potential(0.91 V vs.RHE)and half-wave potential(0.82 V vs.RHE),and hydrogen evolution reaction with the low onset potential(-39 mV vs.RHE),overpotential(56 mV)at the fixed current density of 10 mA cm-2 and small Tafel slope(39 mV dec-1).This is ascribed to the synergistic effects of the bimetals,rGO as the good support and electronic coupling between the Pd-shell and Pt-core.(2)Bimetallic PtPd alloyed core-shell nanodendrites supported on reduced graphene oxide:One-pot green synthesis and efficient electrocatalytic performances for glycerol oxidation and hydrogen evolutionHerein,reduced graphene oxide supported PtPd alloyed core-shell nanodendrites(Pt77Pd23 ACSNDs/rGO)were fabricated by a one-pot aqueous method with the biosynthesized polypeptide(colistin sulfate,CS)as the eco-friendly stabilizer and structure-director.The associated morphology,composition and structure were mainly investigated by a set of characterization techniques,and the synthesis mechanism was discussed in details.When compared with home-made Pt59Pd41 nanoparticles(NPs)/rGO,Ptg9Pd11 NPs/rGO,Pt NPs/rGO,commercial Pt/C and Pd/C catalysts,the prepared nanocomposite exhibited comparable and/or even superior catalytic characters for glycerol oxidation reaction with the higher mass activity(1533.49 mA mg-1 metal)and specific activity(2.74 mA cm-2 metal),and hydrogen evolution reaction with the lower onset potential(-34 mV),smaller overpotential(57 mV)at 10 mA cm-2 and smaller Tafel slope(36 mV dec-1).(3)Simple fabrication of core-shell AuPt@Pt nanocrystals supported on reduced graphene oxide for ethylene glycol oxidation and hydrogen evolution reactionsHerein,we reported the direct synthesis of core-shell AuPt@Pt nanocrystals supported on reduced graphene oxide(AuPt@Pt NCs/rGO)in aqueous media,with poly(1-vinyl-3-ethylimidazolium bromide)(poly(ViEtImBr))as a structure-directing agent,without any specific additive(e.g.,seed,organic solvent,or template).The as-synthesized AuPt@Pt NCs/rGO exhibited improved electrocatalytic performances towards ethylene glycol oxidation reaction in contrast with commercial Pt/C(20 wt.%)catalyst in acidic and alkaline electrolytes.Meanwhile,the catalyst displayed enhanced catalytic activity for hydrogen evolution reaction with the positive onset potential(-25 mV)and a small Tafel slope(33 mV decade-1)relative to Pt/C catalyst(-18 mV,31 mV decade-1)in 0.5 M H2SO4,along with the positive onset potential(-43 mV)and a small Tafel slope(73 mV decade-1)as compared with Pt/C catalyst(-42 mV,85 mV decade-1)in 0.5 M KOH.(4)Dicationic ionic liquid mediated fabrication of Au@Pt nanoparticles supported on reduced graphene oxide with highly catalytic activity for oxygen reduction and hydrogen evolutionIonic liquids as templates or directing agents have attracted great attention for shaping-modulated synthesis of advanced nanomaterials.In this work,reduced graphene oxide supported uniform core-shell Au@Pt nanoparticles(Au@Pt NPs/rGO)were fabricated by a simple one-pot aqueous approach,using N-methylimidazolium-based dicationic ionic liquid(1,1-bis(3-methylimadazoilum-1-yl)butylene bromide,[C4(Mim)2]2Br)as the shape-directing agent.The morphology evolution,structural information and formation mechanism of Au@Pt NPs anchored on rGO were investigated by a series of characterization techniques.The obtained nanocomposites displayed superior electrocatalytic features towards hydrogen evolution reaction and oxygen reduction reaction compared with commercial Pt/C catalyst.This approach provides a novel route for facile synthesis of nanocatalysts in fuel cells.