Controllable Synthesis Of Porous Gold-platinum Bimetallic Nanomaterials With Enhanced Catalytic Properties

Impending depletion of the fossil fuels as well as ever increasing energy demands have stimulated extensive research on alternative energy conversion and storage technologies including fuel cells.Recently,Three-dimensional porous platinum(Pt)-based nanomaterials,as a promising electrocatalysts in fuel cell,have drawn great attention due to their low density,large specific surface area,high stability,and improved electron mobility.Meanwhile,gold(Au)has also become more attractive owing to its specific characters,such as high oxidation-reduction potential,superior stability,and excellent electron transfer capability.Herein,aiming to construct novel Pt-based nanocatalysts with reduced Pt usage amount and enhanced catalytic property,porous AuPt alloy nanomaterials are prepared based on the porous characters in combination with the nature of Au.Specifically,porous AuPt alloy nanomaterials are fabricated via simple one-pot synthesis methods,with the assistance of some structure-directing molecules from poly(ionic liquid),4-amino-2,6-dihydroxypyrimidine(ADHP),L-histidine,to dynamic hydrogen bubbles.The structure,morphology,and composition of the nanomaterials were examined by a series of characterization technologies containing scanning electron microscope(SEM),transmission electron microscopy(TEM),high-angle annular diffraction field-scanning transmission electron microscopy-energy dispersive X-ray spectroscopy(HAADF-STEM-EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The formation mechanisms of the porous AuPt nanomaterials were also investigated in depth.In addition,the as-prepared bimetallic nanomaterials exhibited excellent electrochemical properties including the oxidation of alcohols,the reduction of oxygen,and the evolution of hydrogen in contrast with commercial Pt black or Pt/C,owing to the specific porous structures and synergetic effects between the bimetals.The main contents are as follows:1)Poly(ionic liquid)assisted synthesis of hierarchical gold-platinum alloy nanodendrites with high electrocatalytic properties for ethylene glycol oxidation and oxygen reduction reactionsA facile one-pot method is developed to prepare three-dimensional(3D)hierarchical AuPt alloy nanodendrites(AuPt NDs)with the assistance of poly(ionic liquid)as the green shape-regulator and stabilizer.The as-synthesized architectures show enlarged electrochemically active surface area,and enhanced maximum mass activity(3960 mA mg-1pt)for ethylene glycol oxidation reaction(EGOR)in alkaline media.Furthermore,the as-synthesized AuPt NDs exhibit superior catalytic activity toward oxygen reduction reaction(ORR)in 0.1 M HClO4 via the four-electron pathway,owing to the unique nanostructures as well as the synergistic effects between Au and Pt.2)4-amino-2,6-dihydroxypyrimidine-assisted fabrication of uniform AuPt nanodendrites as efficient electrocatalyst for oxygen reduction and hydrogen evolution reactionsWe present an ultrasonication-assisted wet-chemical method for facile synthesis of uniform bimetallic AuPt alloy nanodendrites(NDs),using 4-amino-2,6-dihydroxypyrimidine as the structure-directing and dispersing agents,without any template,seed,organic solvent or polymer.The structure,morphology,size,and composition of the as-obtained nanocrystals are examined by a series of characterization techniques.The architectures display remarkable catalytic performances toward oxygen reduction and hydrogen generation in comparison to commercial Pt black and Pt/C catalysts,through the polarization,chronoamperometry,and durability measurements.This is due to the special dendritic nanostructures with rich surface defects and porous features and the synergistic effects between Pt and Au in the alloy.In combination with the simple,easily controllable,and time-saving synthetic strategy,AuPt NDs may find potential applications and shed some light on the construction of other bimetallic nanocatalysts in fuel cells.3)Amino acid-assisted fabrication of uniform dendrite-like PtAu porous nanoclusters as highly efficient electrocatalyst for methanol oxidation and oxygen reduction reactionsAmino acid-assisted strategy was designed to construct uniform dendrite-like PtAu porous nanoclusters(PtAu PNCs)by a simple wet-chemical method,where L-histidine served as the structure director and poly(vinylpyrrolidone)(PVP)as the dispersing agent.We mainly investigated the structure,composition,formation mechanism and electrocatalytic performance of PtAu PNCs.By virtue of the bimetallic synergetic effects and unique structures,the architectures exhibited enhanced catalytic activity and durability for methanol oxidation reaction(MOR)and oxygen reduction reaction(ORR)in contrast with non-porous PtAu nanocrystals,Au nanocrystals,porous Pt nanoparticles and commercial Pt black catalysts.4)Hydrogen bubbles template-directed synthesis of self-supported AuPt nanowire networks for improved ethanol oxidation and oxygen reduction reactionsWe present an ultra-simple one-pot aqueous solution method for facilely synthesis of surface-clean and self-supported bimetallic AuPt nanowire networks(AuPt NWNs)with tunable compositions by using hydrogen bubble as a dynamic template.The AuPt NWNs are easily obtained on a large scale,just rapidly pouring sodium borohydride into and metal precursor solutions,where only two kinds of reactants(metal precursors and reductant)are involved without extra polymer,surfactant,seed or pre-made template.Hydrogen bubbles are in situ generated from the hydrolysis and oxidation of sodium borohydride in the synthetic process.The strategy is very simple,rapid,convenient,mild and green,exempted from pressuring,heating,special apparatus and ambience.The AuPt NWNs are surface clean due to without using polymer and surfactant.The gas bubble template-directed synthesis method does not need to use additional acid/base or organic solvent to remove templates.Moreover,the as-prepared AuPt NWNs display excellent electrocatalytic activity and durability toward ethanol oxidation and oxygen reduction reactions.This approach provides an additive-free and green method to facilely synthesize highly active bimetallic nanocrystals on a large scale,which would have promising applications in fuel cells,fine chemical synthesis and sensors.