The Effects Of Composition And Structure Of Pt/GNs Based Catalysts On Their Electrocatalysis For Methanol Oxidation

In this paper, two-dimensional graphene nanosheets （GNs） were used as support materials to introduce transition metal oxide SnO₂, precious metal Pd or non-precious metal Bi into Pt/GNs catalysts. The component structure and morphologies of as-prepared ternary nanocomposites were effectively tuned by soluble macromolecule （PDDA or PVP） or complexing agent （EDTA）. The effects of constituents and structure of catalysts on their electrocatalysis for methanol oxidation （MOR） were discussed, and the main contents are summarized as following.Three different types of composites in this work were designed and synthesized, which are listed as Pt/SnO₂/GNs composites synthesized by hydrothermal reduction method, Pd@Pd/GNs composites and Pt-Bi/GNs composites synthesized by aqueous solution synthesis method, respectively. The components, constructions and morphologies of the composites were characterized by TEM, XRD, XPS, ICP and Raman spectra. The results show that the soluble macromolecule （PDDA or PVP） or complexing agent （EDTA） exert a significant impact on the catalyst structure and morphologies. EDTA can effectively control the co-existence mode of Pt with SnO₂ on the surface of graphenes, leading to the close contact and good coexistence between Pt and SnO₂. The soluble polymer （PDDA and PVP） with their unique structures can significantly affect the morphology and structure of metal nanoparticles on bimetallic catalysts. Electrocatalytic properties of as-synthesized composites for MOR were evaluated by cyclic voltammetry （CV）, chronoamperometry, COaa stripping voltammetry and electrochemical impedance spectrum （EIS）. The results show that the as-synthesized composites Pt/SnO₂/GNs （EDTA） exhibit remarkably improved electrocatalytic performances compared with the commercially available Johnson Matthey Pt/C catalyst （Pt/C-JM）. Especially under the light irradiation, the catalytic activity, anti CO poisoning and stability of Pt/SnOVGNs （EDTA） drastically increase due to the existence of photosensitivity species, which stems from the synergistic effect between the electro-catalytic and photo-catalytic properties. And as-synthesized composites Pd@Pt/GNs （PDDA） and Pt-Bi/GNs （PVP） exhibit remarkably improved electrocatalytic performances compared with Johnson Matthey Pt/C-JM or 30%PtRu/C catalyst （PtRu/C-JM） due to the unique morphologies and structures of bi-metallic catalysts.