Flame synthesis of carbon nanofibers on carbon paper: Physicochemical characterization and application as catalyst support for methanol oxidation Mohsen Khosravi, Mohammad K. Amini * Chemistry Department, University of Isfahan, Isfahan 81746-73441, Iran ARTICLE INFO Article history: Received 28 October 2009 Accepted 26 April 2010 Available online 4 May 2010 ABSTRACT We developed a simple, rapid and highly efficient flame synthesis method for direct grow- ing carbon nanofibers (CNFs) on carbon paper (CP) using a common laboratory ethanol flame as both heat and carbon sources. High density CNFs with tangled solid-cored struc- ture were uniformly formed over the Ni-plated CP surface in 20 s. The morphologies of the CNFs were characterized by scanning electron microscopy and transmission electron microscopy. X-ray diffraction study revealed the graphitic nature of the CNFs. Raman spec- troscopy analysis confirmed that the CNFs are disordered graphitic nanocrystallites with high degree of exposed edges. Electrochemical impedance spectroscopy and cyclic voltam- metry were used to show that growing CNFs directly on CP facilitates electron transfer with concomitant increase in double-layer capacitance. The CNF/CP was used as support for Pt nanoparticles to study their supporting effect on the catalyst performance. The as prepared Pt/CNF electrocatalyst exhibited much improved electrocatalytic activity for methanol oxi- dation compared to Pt/CP and commercial Pt/C on CP. High electronic conductivity and improved electrochemical behavior of the CNF/CPs, resulted from direct contact of the nanofibers with CP, combined with unique properties of CNFs, make the synthesized CNF/CPs promising for fuel cell applications. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Among clean energy-converting devices, polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), have received considerable attention because of their high efficiency, high energy density, low or zero emis- sion, and their potential use in transportation and portable electronic devices. However, one of the major challenges to- wards commercialization of these fuel cells is high cost of Pt currently used as the state-of-the-art electrocatalyst in fab- rication of the membrane electrode assemblies (MEAs). Decreasing the amount of Pt catalyst used in MEAs via increasing its utilization efficiency has been one of the major concerns during the past decade [1]. The utilization efficiency of a catalyst depends significantly on its particle size and dis- persion pattern over the support structure. It is well known that the physical properties of the support can greatly influence the electrochemical properties of the fuel cell catalysts [2]. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs), because of their exceptional surface struc- tures, high electrical conductivities, large surface areas, and high mechanical, chemical and electrochemical stabilities, have been utilized as novel supports for metal catalysts [3]. These materials not only enable high dispersion of catalyst nanoparticles, but also facilitate electron transfer and allow fast mass transport of reactants and products at the fuel cell electrodes, resulting in better device performance [4]. Unlike CNTs, in which graphene sheets are rolled over on them- 0008-6223/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2010.04.050 * Corresponding author: Fax: +98 311 6689732. E-mail address: mkamini@chem.ui.ac.ir (M.K. Amini). CARBON 48 (2010) 3131 – 3138 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon