Please cite this article in press as: A. Esmaeilifar, et al., Preparation of low-platinum-loading electrocatalysts using electroless deposition method for proton exchange membrane fuel cell systems, Electrochim. Acta (2010), doi:10.1016/j.electacta.2010.08.084 ARTICLE IN PRESS G Model EA-16203; No. of Pages 7 Electrochimica Acta xxx (2010) xxx–xxx Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Preparation of low-platinum-loading electrocatalysts using electroless deposition method for proton exchange membrane fuel cell systems Ashkan Esmaeilifar a , Soosan Rowshanzamir a,b,∗ , Mohammad H. Eikani c , Ehsan Ghazanfari a a Fuel Cell Laboratory, Green Research Center, Iran University of Science and Technology, Narmak, Tehran, Iran b School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran c Department of Chemical Industries, Iranian Research Organization for Science & Technology (IROST), Tehran, Iran article info Article history: Received 8 May 2010 Received in revised form 21 August 2010 Accepted 21 August 2010 Available online xxx Keywords: Electroless deposition Platinum loading Electrocatalyst performance Proton exchange membrane fuel cell Electrocatalyst synthesis abstract One promising preparative method that offers the potential for improved platinum (Pt) dispersion of electrocatalysts is electroless deposition (ED). In this study, the effects of multiwalled carbon nanotubes (MWCNTs) pretreatment and synthesis procedure on properties of the four catalysts, synthesized by ED method, have been considered. The results of energy-dispersive X-ray spectroscopy (EDS), X-ray dot- mapping, X-ray fluorescence (XRF) and cyclic voltammetry (CV) analyses showed that using palladium (Pd) precursor during two-step sensitization–activation coating procedure gives uniform Pt particles distribution on MWCNTs with low aggregation and high specific surface area (∼80 m 2 g -1 ). In addition, to investigate the performance of the synthesized catalysts in experimental fuel cell system, thin-film method was used to fabricate the membrane electrode assemblies (MEAs). Obtaining the polarization curves for the fabricated MEAs (Pt loading ∼0.4 mg cm -2 ) and a commercial MEA (ElectroChem, Pt load- ing ∼1 mg cm -2 ) demonstrated that the catalyst prepared by two-step sensitization–activation coating procedure possesses a good performance despite of its lower Pt content. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction With the growing commercialization of fuel cells and subse- quent attempts to make the technology economically competitive, much attention has been focused on lowering the cost of the mem- brane electrode assembly (MEA) and, specifically, the catalysts used for the oxygen reduction reaction (ORR). The most common elec- trocatalyst used in proton exchange membrane (PEM) fuel cells is Pt supported on electrically conductive porous carbon. One way to lower the cost of Pt in fuel cells is to minimize the particle sizes of the supported Pt catalyst and thereby increase the sur- face/volume ratio of the Pt particles (Pt dispersion) to achieve a more efficient use of Pt. One promising preparative method that offers the potential for improved Pt dispersion is electroless depo- sition (ED). ED is a catalytic or auto-catalytic process whereby a chemical reducing agent reduces a metallic salt onto specific sur- face sites which can either be a catalytically active substrate [1] or an inert substrate seeded with a catalytically active metal [2]. This ED methodology, an alternative to electroplating of substrates, is also referred to as electroless plating. Plating generally involves creating thin (on the order of several microns) homogeneous, metal ∗ Corresponding author at: Iran University of Science and Technology, Green Research Center, Fuel Cell Laboratory, Tehran, Iran. Tel.: +98 21 77491242; fax: +98 21 77491242. E-mail address: rowshanzamir@iust.ac.ir (S. Rowshanzamir). layers and has many applications in various fields such as electron- ics, wear and corrosion-resistant materials, medical devices, and battery technology [3]. Thus, even though electrolessly deposited platinum has become commonplace in the plating industry for sit- uations where conventional electrical deposition is not sufficiently uniform [4–6], selective and controlled deposition, as opposed to continuous plating, has just recently been examined [7–9] for appli- cations in catalysis. The overall reaction for ED is a combination of anodic and cathodic electrochemical partial reactions [3,4]. Reac- tion (1) is the overall reaction, while (2) and (3) are the anodic and cathodic partial reactions: N + M z+ (aq) + RA(aq) → M–N + Ox(aq) (1) RA(aq) → Ox(aq) + ze - (2) N + M z+ (aq) + ze - → M–N (3) respectively in the above reactions, Ox is the oxidation product of the reducing agent (RA) and M is the metallic form of the reducible metal salt (M z+ ) that has been deposited on the catalytic nuclei (N) which has already been deposited on the carbon support. From an electrochemical standpoint, the equilibrium potential of reac- tion (2) must be more negative than the equilibrium potential of reaction (3). According to the mixed potential theory, the overall system reaches an equilibrium mixed potential E mp during steady state which is found by equating the currents of the two partial reactions. A further corollary of the above equations is that the site 0013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2010.08.084