Journal of Power Sources 138 (2004) 14–24 Preparation of PEM fuel cell electrodes using pulse electrodeposition Hansung Kim, Nalini P. Subramanian, Branko N. Popov ∗ Center for Electrochemical Engineering, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA Received 7 April 2004; accepted 9 June 2004 Available online 5 August 2004 Abstract A new approach based on pulse electrodeposition is demonstrated to be an attractive technique to replace conventional powder type membrane electrode assembly (MEA) preparation methods. The performance of the catalyst layer is optimized by controlling the pulse deposition parameters such as the peak current density, duty cycle and the total charge density. The peak current density and the pulse duty cycle are found to control the nucleation rate and decrease the catalyst dendric growth. The amount of platinum loading is controlled by the total charge density. Preparing the electrode using a peak current density of 400 mA/cm 2 , a duty cycle of 2.9% and a total charge density of 8 C/cm 2 results in a high catalyst performance of 380 mA/cm 2 at 0.8 V. © 2004 Elsevier B.V. All rights reserved. Keywords: Fuel cell; Pulse electrodeposition; Off time; Cyclic voltammetry 1. Introduction Polymer electrolyte membrane (PEM) fuel cells offer low weight and high power density and are being considered for automotive and stationary power applications [1–4]. Cur- rent approaches for preparing a membrane electrode assem- bly (MEA) for PEM fuel cells can be broadly divided into two different categories—powder type and non-powder type. The powder type involves the process of catalyzation on a high surface area of carbon. The prepared carbon supported catalyst is mixed with binder and then applied to the mem- brane followed by gas diffusion layer (GDL) addition or to the GDL followed by membrane addition. Ulchida et al. [5] prepared a colloid mixture containing Pt/C powder, perflu- orosulfonate ionomers (PFSI, such as Nafion) and solvent using ultrasonic treatment. This paste was then spread over the wet-proofed gas diffusion layer of carbon paper. The electrodes with the paste on it were hot-pressed to both sides of a membrane to fabricate an MEA. The observed increase in MEA performance was attributed to the increase in con- tact area between the PFSI and the Pt particles. Wilson and Gottesfeld developed a catalyst decaling process in order to produce a dense and thin catalyst layer [6,7]. The first step in this process is preparing ink containing Pt/C powder, Nafion ∗ Corresponding author. Tel.: +1-803-777-7314; fax: +1-803-777-8265. E-mail address: popov@engr.sc.edu (B.N. Popov). solution and solvent. This ink is then applied to a Teflon blank and heated until dry. More layers of Pt/C/Nafion ink are added until the desired catalyst loading is achieved. The catalyst coated Teflon blanks are hot pressed to the Nafion membrane. Then, the Teflon blank is peeled away from the membrane, resulting in the MEA. The catalyst layer in powder type MAE has a uniform concentration profile of the catalyst, since the Pt/C powder is thoroughly mixed with the binder before being applied to the membrane or GDL. A high content of Pt in the Pt/C powder allows reducing the thickness of the catalyst layer without sacrificing the catalyst loading per area of electrode. How- ever, it is difficult to control the particle size of the catalyst when the Pt to carbon ratio increases more than 40 wt.%. In order to overcome this limitation, several non-powder type processes were developed. These processes create the catalyst directly on the surface of carbon electrode or membrane. Fedkiw and Her [8] describe a two-step impregnation-reduction method in which the Nafion mem- brane first undergoes an ion exchange reaction with a metal salt, then the impregnated membrane is exposed to a reduc- ing agent to form a catalyst layer directly on the membrane. Another method is evaporative deposition, in which, as described by Foster et al. [9], a Pt salt is evaporated and deposited on a membrane. A third MEA preparation tech- nique is sputtering. Hirano et al. [10] show that a very thin layer of sputter deposited platinum on a wet-proofed GDL performs very similarly to a standard E-TEK electrode. 0378-7753/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2004.06.012