Single-walled carbon nanotube-supported platinum nanoparticles as fuel cell electrocatalysts
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rancisco Alcaide, Larraitz Ganborena, Ione Cendoya, Oscar Miguel, and Javier Rodríguez CIDETEC, Centre for Electrochemical Technologies, Parque Tecnológico de San Sebastián, 20009 Donostia-San Sebastián, Spain
Esteban P. Urriolabeitia and Rafael Navarro Departamento de Química Inorgánica, ICMA (Universidad de Zaragoza-CSIC), 50009 Zaragoza, Spain (Received 28 March 2006; accepted 7 June 2006)
Single-walled carbon nanotubes (SWNTs) have been used as electrocatalyst support for fuel cells. A toluene solution of a platinum salt, bis(dibenzylideneacetone) platinum, has been used for the first time to decorate the outer surface of SWNT bundles with Pt nanoparticles. The obtained Pt/SWNT materials were then used as catalytic layer in electrodes for fuel cell electrocatalysis. The used platinum salt concentration in the initial SWNT dispersion determined the Pt nanoparticle size and, consequently, the activity of the Pt/SWNT electrodes toward the oxygen reduction reaction. The achieved results were compared with those corresponding to a commercial Pt/carbon black catalyst with similar Pt loading and surface area. I. INTRODUCTION
The use of novel nanostructured materials is causing a major impact in fuel cell technology. Thus, the development of new hydrogen storage nanomaterials, nanocomposites for polymeric membranes and carbon plates, and catalyst nanoparticles is being addressed in an increasing number of papers.1–4 Platinum is widely recognized in heterogeneous catalysis and electrocatalysis, especially in fuel cell technology. Pt loading and particle size, as well as the nature of catalyst support, are important issues for the fabrication of electrodes to be efficiently used in electrocatalysis reactions. Conventional preparation techniques based on wet impregnation and chemical reduction of the metal precursors often do not provide adequate control of particle shape and size.5 Consequently, much attention is focused on developing alternative Pt decoration methods based on the use of microemulsions,6,7 sonochemistry,8,9 microwave irradiation,10,11 ion exchange,12 precipitation,13 and colloidal method.14 Although activated carbon is still the most used support material for electrocatalysis, the use of new forms of nanostructured carbonaceous materials such as carbon nanotubes (CNTs) is the focus of considerable research.15–18 CNTs have been envisioned as promising
materials for potential application in many fields because of their remarkable structural, electronic, mechanical, and physical properties.19,20 Because of their high aspect ratio, high electrochemically accessible area, porous structure, and high chemical stability, CNTs are interesting materials to be used as catalyst supports if methods are developed for efficiently decorating the outer CNT surface with catalytically active metal nanoparticles.4,21–28 Thus, Pt-decorated CNTs are being successfully used as supports for efficient Pt catalysis processes because the electrocatalytic mass activity of Pt dispersed in CNTs can be significantly higher than that
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