One-pot Wet-chemical Route For Controllable Synthesis Of Platinum-silver Nanocomposites And Their Electrocatalysis Research

Fuel cells have drawn enormous attention due to their environmental friendliness and high energy density.Catalysts play an important role in fuel cells.Among them,platinum(Pt)catalysts have the broad applications due to their remarkable catalytic activity.Recently,Pt-based nanomaterials confirmed the better electrocatalytic activity in fuel cells than that of single Pt catalyst.Meanwhile,silver(Ag)has also become more attractive owing to its superior electrical conductivity,strong poison resistance,high stability and excellent electron transfer ability.Therefore,aiming to construct novel Pt-based nanocatalysts with reduced Pt usage amount and enhanced catalytic property,we carried out some new explorations in the controllable synthesis of PtAgnanocomposites with various structures and high catalytic activity.Herein,we synthesized and characterized three kinds of PtAg nanocomposites by a simple one-pot aqueous method using L-Hydroxyproline,Diprophylline and 1,4-bis(pyridinium)butane dibromide as the structure-directors and stabilizing agents.The formation mechanism,electrocatalytic properties and stability of the three materials were examined.The results show that the PtAg nanocomposites have better catalytic activity and stability than commercial Pt/C,Pt black and single Pt catalysts.The specific contents are as follows:(1)Dendrite-like PtAg alloyed nanocrystals:highly electrocatalytic and durable advanced catalyst for oxygen reduction and ethylene glycol oxidation reactionsWell-defined dendrite-like PtAg alloyed nanocrystals were prepared by a facile one-pot L-Hydroxyproline-assisted successive coreduction approach on a large scale,where no any template or seed involved.The as-prepared frameworks exhibited boosted electrocatalytic activity,improved stability and enhanced tolerance toward oxygen reduction reaction and ethylene glycol oxidation reaction in alkaline media in contrast with commercial Pt black catalyst,owing to their unique structure as well as the synergistic effects between Ag and Pt.The developed method provides novel strategy for preparing other shape-controlled nanocatalysts with superior catalytic activity and durability in fuel cells.(2)Simple one-pot synthesis of solid-core@porous-shell alloyed PtAg nanocrystals for the superior catalytic activity toward hydrogen evolution and glycerol oxidationSolid-core@porous-shell alloyed PtAg nanocrystals(PtAg NCs)were fabricated via a simple one-pot co-reduction wet-chemical method on a large scale.Diprophylline was employed as the stabilizing agent and shape-directing agent,without any surfactant,polymer,seed or template.The products were mainly analyzed by a series of characterization techniques.The hierarchical architectures had enhanced stability and improved electrocatalytic activity for hydrogen evolution reaction and glycerol oxidation reaction in contrast with commercial available Pt/C and Pt black catalysts.For the prepared PtAg NCs catalyst,the Tafel slope is 40 mV dec-1 toward hydrogen evolution reaction in 0.5 M H2SO4,coupled wth the specific activity and mass activity of 3.23 mA cm-2 and 1303 mA mg-1pt toward glycerol oxidation reaction,respectively.These results demonstrate that the as-prepared nanocatalysts have promising applications in fuel cells.(3)One-pot aqueous fabrication of reduced graphene oxide supported porous PtAg alloy nanoflowers to greatly boost catalytic performances for oxygen reduction and hydrogen evolutionReduced graphene oxide supported porous PtAg alloy nanoflowers(PtAg NFs/rGO)were synthesized by a simple one-pot aqueous method using pyridinium-based dicationic ionic liquid(1,4-bis(pyridinium)butane dibromide)as the new structure-director and stabilizing agent.The products were characterized by a series of techniques.The obtained nanocomposite had more positive onset potential(1.03 V)for oxygen reduction reaction in alkaline electrolyte than those of commercial Pt/C(0.96 V)and home-made Pt nanoparticles(NPs)/rGO(Pt NPs/rGO,0.97 V),showing the enhanced catalytic performance for hydrogen evolution reaction with the positive onset potential(-26 mV)and a small Tafel slope(31 mV dec-1)relative to Pt NPs/rGO(-42 mV,36 mV dec-1)in 0.5 M H2SO4.The nanocomposite displayed the increased catalytic capacity and improved stability in comparison to Pt/C towards oxygen reduction reaction in 0.1 M KOH and hydrogen evolution reaction in 0.5 M H2SO4.This is ascribed to the unique structure of PtAg NFs,the synergetic effects of Pt and Ag,along with the introduction of rGO as the good support.