Design&Synthesis Of Pt/3D-GNs Composites And Their Electrocatalysis For Methanol Oxidation

So far,Pt/graphene based catalyst is the main research focus using as direct methanol fuel cell(DMFC)anode catalyst,but it still has many shortcomings in practical application.On one hand,Pt has low methanol electro-oxidation kinetics and vulnerability toward poisoning by intermediate products;on the other hand,graphene is more stable physically and chemically resulting in surface inertia,which does not contribute to the metal load on the graphene.All of those drawbacks restricted the wide practical application of Pt/graphene based anodic catalysts in DMFC.In order to solve above problems,we use two-dimensional(2D)plane structure of graphene as a substrate to build three-dimensional graphene(3D-GNs)with porous structure through different methods,which makes electro-chemical properties of graphene combine with properties of porous materials to obtain an excellent support material.Furthermore,the introduction of third component into Pt/3D-graphene based catalyst can optimize the performance of Pt and 3D-graphene,effectively reduced the oxidation potential of methanol,providing a new composite catalyst material for the development and application of DMFC.Concretely speaking,in this paper,the 3D-GNs were used as support materials and select carbon black(Vulcan XC-72R),conductive polymer polyaniline(PANI)and transition metal indium(In),respectively as the third component to be introduced into Pt/3D-GNs catalysts.So that three different types of composites were designed and synthesized.Namely,Pt/3D-GNs(C)composite was synthesized by reflux combined with liquid nitrogen frozen,Pt/3D-GNs(PANI)composite was synthesized by one pot hydrothermal reduction and PtIn/3D-GNs composite was synthesized by solid phase synthesis method.The components,constructions and morphologies of the composites were characterized by SEM,TEM,XRD,XPS,ICP and Raman spectra.Electrocatalytic properties of as-synthesized composites for MOR were evaluated by cyclic voltammetry(CV),chronoamperometry,COad stripping voltammetry and electrochemical impedance spectrum(EIS).The investigation results show that the graphene in Pt/3D-GNs(C)(1),Pt/3D-GNs(PANI)(2)and PtIn/3D-GNs(3)composites possesses three-dimensional porous structure.These three composites as electrocatalysts exhibit remarkably improved electrocatalytic performances compared with the commercially available Johnson Matthey Pt/C catalyst(Pt/C-JM).In(1),Vulcan XC-72R carbon black combined with 3D-GNs can increase the adsorption rate of the metal precursor and provide more attachment sites for the loading of Pt particles to improve dispersion of the metal;In(2),polyaniline(PANI)can significantly affect the morphology and structure of metal nanoparticles in the catalyst,the Pt nanoparticles in Pt/3D-GNs(PANI)were small and uniform with the modification of PANI polymerized in-situ;In(3),it is first time to introduce photosensitive indium into platinum to prepare bimetallic catalyst which remarkably enhanced the catalytic activity toward methanol oxidation reaction and anti-poisoning ability.Especially,under external light irradiation,Pt-In/3D-GNs composite presents a significant electro-photo synergistic catalysis effect for MOR.