Applied Catalysis A: General 407 (2011) 195–203 Contents lists available at SciVerse ScienceDirect Applied Catalysis A: General j ourna l ho me page: www.elsevier.com/locate/apcata Synthesis of Pt–Co nanoparticles on multi-walled carbon nanotubes for methanol oxidation in H 2 SO 4 solution R.S. Amin a , K.M. El-Khatib a , R.M. Abdel Hameed b,∗ , Eglal R. Souaya c , Mohamed A. Etman d a Chem. Eng. & Pilot Plant Dept., Engineering Division, National Research Center, Dokki, Giza, Egypt b Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt c Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt d Housing and Building National Research Center (HBRC), El-Tahrir St., Dokki, Giza, Egypt a r t i c l e i n f o Article history: Received 16 July 2011 Received in revised form 25 August 2011 Accepted 26 August 2011 Available online 3 September 2011 Keywords: Platinum–cobalt Methanol oxidation Fuel cells MWCNTs Electrocatalyst a b s t r a c t Pt and Pt–Co supported on MWCNTs were synthesized by the impregnation method using NaBH 4 as the reducing agent. The effect of varying NaBH 4 concentration on particle size, morphology and chem- ical composition of Pt–Co/MWCNTs was studied. A homogeneous distribution of Pt–Co nanodeposits with particle size of 2–5 nm was attained in TEM images at Pt–Co/MWCNTs “×70” powder. EDX analysis confirmed the reduction of higher amount of Co in Pt–Co/MWCNTs “×40” electrocatalyst. The electro- chemical activity of Pt/MWCNTs and Pt–Co/MWCNTs electrocatalysts was examined towards methanol oxidation reaction in 0.5 M H 2 SO 4 solution by employing the cyclic voltammetry and the chronoamper- ometry techniques. The lowest onset potential and the highest oxidation current density were gained at Pt–Co/MWCNTs “×70” electrocatalyst. Its good stability over the long-term performance study elects it as a promising candidate for the DMFCs applications. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Nanotechnology has recently been applied to direct methanol fuel cells (DMFCs); one of the most suitable and promising options for portable devices. With characteristics such as low working tem- perature, high energy-conversion efficiency and low emission of pollutants, DMFCs may help to solve the future energy crisis [1]. However, their commercial viability is still hindered by several factors, including the low catalytic activity of the electrodes, the high cost of the Pt-based electrocatalysts and their susceptibility to be poisoned by the CO-like intermediates formed in the methanol oxidation reaction [2–6]. The development of bimetallic catalysts usually consists of a pri- mary metal that has a high catalytic activity and a secondary metal that can enhance the catalytic activity or prevent the poisoning problems. Currently, the benchmark anode catalyst for DMFCs is Pt–Ru. It shows a significant activity for methanol oxidation as well as the dehydrogenation of water which is critical for the removal of adsorbed CO species [7–10]. However, it can’t be applied on the commercial scale due to its prohibitively high cost and limited supply. As a result, the preparation of non-precious alternatives to Pt–Ru catalysts became a must. Pt–Co alloys have been exam- ∗ Corresponding author. Tel.: +20 2 35736877. E-mail address: randa311eg@yahoo.com (R.M.A. Hameed). ined as excellent CO-tolerant anode catalysts as well as Pt–Fe, Pt–Ni and Pt–Mo [11–13]. Generally, it was found that the addition of Co promoted a more efficient initiation of methanol dehydrogenation, resulting in better performance for MOR in terms of the Faradic cur- rent compared to Pt/C [14]. Moreover, Pt withdraws electrons from Co atoms to increase the amount of Pt 0 species in Pt–Co/C [15]. In addition to the variety of the nanoparticles being synthe- sized, the choice of the suitable carbon support material is also an important factor that can significantly affect the electrocatalytic activity owing to its interaction with the metal catalyst [16]. For this purpose, conductive carbon black powders, such as Vulcans, are commonly used. A new generation of catalyst supports, based on carbon nanomaterials, has also been developed [17–22]. It involves carbon nanotubes, carbon nanofibers, carbon nanocoils and car- bon nanohorns. They have distinctive characteristics, compared to conventional carbon black, such as more crystalline structure with high electrical conductivity, excellent corrosion resistance and high purity with less catalyst poisons [23–26]. Because of the pristine structure of CNTs, it is difficult to attach metal nanoparticles to their surface. This problem could be solved by surface pre-treatment to introduce some anchoring sites to facil- itate the nanoparticles deposition [27–29]. Several methods have been adopted to prepare highly dispersed metal/CNTs catalysts, e.g., electro-deposition [30] and supercritical fluid reaction [31]. The conventional impregnation method is simple and it depends on the chemical reduction via a certain reducing agent [32–34]. The 0926-860X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2011.08.045