Journal of Power Sources 195 (2010) 7409–7414 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour KOH-activated multi-walled carbon nanotubes as platinum supports for oxygen reduction reaction Chaoxiong He a , Shuqin Song a,∗ , Jinchao Liu a , Vasiliki Maragou b , Panagiotis Tsiakaras b,∗∗ a State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China b Department of Mechanical Engineering, School of Engineering, University of Thessaly, Pedion Areos, 38834 Volos, Greece article info Article history: Received 1 April 2010 Received in revised form 18 May 2010 Accepted 25 May 2010 Available online 31 May 2010 Keywords: Carbon nanotubes KOH Activation Low platinum ORR catalyst abstract In the present investigation, multi-walled carbon nanotubes (MWCNTs) thermally treated by KOH were adopted as the platinum supporting material for the oxygen reduction reaction electrocatalysts. FTIR and Raman spectra were used to investigate the surface state of MWCNTs treated by KOH at different temperatures (700, 800, and 900 ◦ C) and showed MWCNTs can be successfully functionalized. The struc- tural properties of KOH-activated MWCNTs supported Pt were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their electrochemical performance was evaluated by the aid of cyclic voltammetry (CV) and rotating disk electrode (RDE) voltammetry. According to the experimental findings of the present work, the surrface of MWCNTs can be successfully functionalized with oxygen-containing groups after activation by KOH, favoring the good dispersion of Pt nanoparti- cles with narrow size distribution. The as-prepared Pt catalysts supported on KOH treated MWCNTs at higher temperature, possess higher electrochemical surface area and exhibit desirable activity towards oxygen reduction reaction (ORR). More precisely, it has been found that the electrochemical active area of Pt/MWCNTs-900 is approximately two times higher than that of Pt/MWCNTs. It can be concluded that KOH activation is an effective way to decorate MWCNTs’ surface with oxygen-containing groups and bigger surface area, which makes them more suitable as electrocatalyst support materials. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Proton exchange membrane fuel cells (PEMFCs) systems are a type fuel cell developed for transport applications as well as for small-scale stationary and portable fuel cell applications [1]. Their advantages include the environmental friendly and low tempera- ture operation, as well as quick start-up and shut-down procedures. In the specific operation system, hydrogen is considered as the preferred fuel in virtue of its high activity and its environmen- tal benignity. Along with the PEMFCs development, low molecular alcohols (especially methanol and ethanol) are also directly fed into the anode as the fuel because of the easy handle of liquid fuel and their high power density [2]. Whatever the case may be, Pt or Pt- based binary or ternary catalysts are still the well-known catalyst materials providing desirable performance for electrode reactions. To make full use of Pt and reduce Pt usage, Pt-based catalysts are usually dispersed on carbon supports with high surface area. How- ever, with the coexistence of Pt, the corrosion of carbon supports ∗ Corresponding author. Tel.: +86 20 84113253; fax: +86 20 84113253. ∗∗ Corresponding author. Tel.: +30 24210 74065; fax: +30 24210 74050. E-mail addresses: stsssq@mail.sysu.edu.cn (S. Song), tsiak@mie.uth.gr (P. Tsiakaras). will be accelerated especially at the cathode, and in this way, the Pt nanoparticles will be aggregated into a big one, leading to the activity loss of Pt [3,4]. On the other hand, with the development level of PEMFCs sys- tem, the total Pt storage in the world would be depleted if each car, which is powered by a 100 kW fuel cell stack, needs 100 g Pt [5]. One and a half billion cars will need 150,000 ton of Pt, which is far more than the estimated Pt resources in the world (28,000 ton) [3], let alone the other wide application of Pt in the area of catal- ysis, jewellery and so on. Based on this, the challenging issue of the high catalyst cost resulting from the exclusive adoption of Pt or Pt-based catalysts must be addressed, and in this way to pro- mote the commercial viability of PEMFCs. A fundamental solution in this direction is the adoption of low Pt catalysts for fuel cell reac- tions. For this purpose, recently, many efforts have been oriented towards the development of new oxygen reduction reaction (ORR) electrocatalysts with lower Pt loadings supported on carbon nan- otubes, focusing at the same time on the synergistic effect between catalyst and support. Carbon nanotubes (CNTs) are a kind of one-dimensional carbon materials, which is nano level in the radial size and micron level in the axial size. For the use as catalyst support, the typical character- istics of CNTs correspond to 10–50 nm for the outer diameter, and 3–15 nm for the inner diameter, while the length ranges from 10 to 0378-7753/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2010.05.050