Nanoscale titania ceramic composite supports for PEM fuel cells
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Titanium-based ceramic supports designed for polymer electrolyte membrane fuel cells were synthesized, and catalytic activity was explored using electrochemical analysis. Synthesis of high surface area TiO2 and TiO supports was accomplished by rapidly heating a gel of polyethyleneimine-bound titanium in a tube furnace under a forming gas atmosphere. X-ray diffraction analysis revealed anatase phase formation for the TiO2 materials and crystallite sizes of less than 10 nm in both cases. Subsequent disposition of platinum through an incipient wetness approach leads to highly dispersed crystallites of platinum, less than 6 nm each, on the conductive supports. Scanning Electron Microscope (SEM)/energy dispersive x-ray analysis results showed a highly uniform Ti and Pt distribution on the surface of both materials. The supports without platinum are highly stable to acidic aqueous conditions and show no signs of oxygen reduction reactivity (ORR). However, once the 20 wt% platinum is added to the material, ORR activity comparable to XC-72-based materials is observed. I. INTRODUCTION
Polymer electrolyte membrane (PEM) fuel cells are a leading technology for transportation and other portable applications, but significant technical barriers make full commercialization of this technology elusive. Two major road blocks are degradation of the carbon support by corrosion and electrochemical surface area loss, both of which lead to high costs and reduced performance. Durability work has demonstrated the detrimental effects of potential cycling on carbon corrosion,1–5 and Pt particle growth and movement off the support within the catalyst layer are two identified mechanisms of deterioration.6,7 Once the carbon support degrades and Pt particle growth initiates, electrochemical surface area and thus performance are significantly reduced.8 Initial system improvements focused on Pt-black technology9–12 and development of the supported platinum catalyzed membrane approach for fabrication of membrane electrode assemblies.13–15 These efforts increased surface area and reduced platinum loadings to improve overall performance; however, 2015 Department of Energy (DOE) technical targets for platinum loadings (0.20 mg/cm2) and durability will require significant additional advancements in the field. Our recent work presented herein aims to replace the traditional Pt/C catalyst support system by synthesizing a ceramic-based support with less susceptibility to corrosion and increased Pt-support interactions while maintaining high catalytic activity. The importance of PEM fuel cell research has lead to a wide variety of approaches to solve the commercialization a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.169 2046
problems including altering the type of carbon used (typically by graphitization),16,17 replacing the carbon support with conductive ceramic-based support materials (see Refs. 18, 19, and references therein), and synthesizing composites of ceramic and carbonaceous material.18 Improve
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