Graphene Role as Platinum Support for CO and Formic Acid Electrooxidation
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Graphene Role as Platinum Support for CO and Formic Acid Electrooxidation Shirui Guo1#, Huseyin Sarialtin2#, Shaun Alia4, Hayri Engin Akin3, Yushan Yan4, Cengiz S. Ozkan2*, Mihrimah Ozkan3* 1
Department of Chemistry, 2Department of Mechanical Engineering, 3Department of Electrical Engineering, 4Department of Chemical & Environmental Engineering, University of California, Riverside. # These authors did the same contribution to the paper.
Abstract The direct methanol fuel cell (DMFC) is a promising power source for electronic applications due to its high efficiency and compactness. To improve the efficiency, many support materials have been developed. We investigated uniform graphene nanoflake films as a support for catalytic Pt nanoparticles in direct carbon monooxide and formic acid electro-oxidation. Pt nanoparticles were deposited on the surface of graphene films with chemical reduction method. Chemical functionalization of graphene with ethylenediamine enables Pt nanoparticles mobilize on graphene uniformly. By simply changing the loading amount of Pt precursor, various particle sizes were achieved. The particle size of Pt plays prominent role in fuel cell test. The electrochemically active surface area of different sample are 6.3 (5 wt% Pt/G), 4.1 (20 wt% Pt/G), and 3.0 (50 wt% Pt/G) cm2mg-1 corresponding to the particle size 3±1nm, 10±2nm, 20±2nm respectively. The results obtained are ascribed to a uniform network made of 2-4 nm Pt monolayer nanopaticles on the surface of graphene flakes. Graphene will play significant role in developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy. INTRODUCTION Direct methanol fuel cells (DMFC) have attracted great attentions recently due to its high energy density, low pollutant emission, low operating temperature (60–100◦C), and ease of handling liquid fuel.[1] However, the low electrocatalytic activity of methanol oxidation is still obstacle inhibiting broad application of DMFC. Many support material have been developed as catalyst support, such as carbon black,[2] mesoporous carbon sphere,[3] zeolite,[4] etc. Recently, graphene nanosheets (GSs), which have a two-dimensional carbon nanostructure, were widely studied as a carbon support material for electrocatalysts, energy-storage materials, and polymer composites. This is because GSs have a high thermal conductivity (∼5000 W3 m-1), a high
electrical conductivity, and a high specific surface area. GSs could be prepared by a facile chemical method that readily produces exfoliated graphene sheets from graphite on a large-scale. The products have many defect sites, i.e. sp3 bond from broken sp2 bond, located on the GSs surface. Such defect sites are considered to serve as active sites for chemical reactions. Furthermore, the two-dimensional structure of GSs provides a pathway for access by gas from both sides of the nanosheet. Here, we reported functionalized graphene sheets could be promising support for Pt nanoparticles. And with the reduced amount of catalyst high act
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