Supported and unsupported platinum catalysts prepared by a one-step dry deposition method and their oxygen reduction reactivity in acidic media |
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Authors: | Justin Roller Roberto Neagu Frank Orfino Radenka Maric |
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Affiliation: | 1. Department of Chemical Materials & Biomolecular Engineering, Center for Clean Energy Engineering, University of Connecticut, Storrs, CT, USA 2. National Research Council-Institute for Fuel Cell Innovation, Vancouver, BC, Canada
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Abstract: | The present study examines the physical and electrochemical properties of platinum particles generated by a combustion method
for use in oxygen reduction on the cathode side of a proton exchange fuel cell (PEMFC). This method employs a one-step, open-atmosphere,
and dry deposition technique called reactive spray deposition technology (RSDT). The objective of this study is to characterize
the intrinsic activity of the platinum produced for incorporation into low-loading cathode electrodes in high performing membrane
electrode assemblies (MEA). The process allows for independent real-time control of the carbon, platinum, and ionomer ratios
in the final electrode. In this research work we examine the oxygen reduction reaction via a rotating disk three electrode
set-up to understand the intrinsic activity of the as-sprayed platinum as well as platinum condensed onto a carbon support.
The mass and specific activities were measured in a 0.1 M perchloric acid electrolyte under different deposition conditions
and loading was verified by atomic emission spectroscopy inductively coupled plasma (AES-ICP). Microscopy results indicate
that the platinum particle sizes are 5 nm (σ = 2.8 nm) in diameter while TEM and XRD show that the platinum generated by the
process is pure and crystalline without bulk oxides or precursor material present. The initial rotating disk electrode result
shows that the RSDT technique is capable of producing catalysts with an oxygen reduction mass activity at 0.9 V of 200 mA/mgPt rotating at 1600 rpm and 30 °C. The electrochemically active surface area approaches 120 m2/g for the platinum, carbon, and ionomer samples and the unsupported sample with only platinum has an active area of 92 m2/g. The rather larger surface area of the unsupported sample exists when the platinum is deposited as a highly porous nanostructured
layer that allows for high penetration of reactant. |
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