Catalysis Today 67 (2001) 15–32 PEM fuel cell as a membrane reactor Tony Thampan a , Sanjiv Malhotra b , Jingxin Zhang a , Ravindra Datta a,∗ a Department of Chemical Engineering, Fuel Cell Center, Worcester Polytechnic Institute, Worcester, MA 01609, USA b H Power Corp., 60 Montgomery Street, Belleville, NJ 07109, USA Abstract The H 2 –O 2 proton-exchange membrane (PEM) fuel cell, among numerous other potential applications now slated to provide the motive power for the next generation of highly efficient and largely pollution-free automobiles, is an incomparable membrane reactor, comprising an exquisitely designed membrane-electrode-assembly (MEA), a five-layer composite of two gas-diffusion layers, two supported-catalyst layers, and a PEM. The device allows catalytic reaction and separation of hydrogen and oxygen as well as protons and electrons. This paper describes the structure and performance of the PEM fuel cell considered as a membrane reactor and develops an analytical transport–reaction model that, despite some assumptions, captures the essential features of the device very well. The key assumptions are that transport resistance as well as ohmic drop are negligible in the catalyst layer. While the latter is defensible, the former causes deviations at high current densities. Nonetheless, the model predicts the fuel cell performance well with parameter values reported in the literature. © 2001 Published by Elsevier Science B.V. Keywords: Proton-exchange membrane; Membrane-electrode-assembly; Transport–reaction model; Fuel cell 1. Introduction Fuel cells offer the potential of revolutionizing elec- trical energy production by affording highly efficient and largely pollution-free power generation systems for both transportation and stationary applications [30,46]. Proton-exchange membrane (PEM) fuel cells [27], operating on H 2 and O 2 (from air), are the focus at this time, although other fuel cells, namely, molten carbonate fuel cells (MCFCs), solid-oxide fuel cells (SOFCs) and direct methanol fuel cells (DMFCs) also hold promise for various applications [7,34]. The PEM fuel cell is particularly attractive because of mild operating conditions (50–80 ◦ C temperature, 1–3 atm pressure), low Pt loadings, relative robustness, long ∗ Corresponding author. Tel.: +1-508-8315250; fax: +1-508-8315853. E-mail address: rdatta@wpi.edu (R. Datta). life, and the fact that all of its components are solid. It comprises an intricate membrane-electrode-assembly (MEA), a five-layer composite of two gas-diffusion layers that allow simultaneous transport of gases and water while collecting current, two three-phase supported-catalyst (typically Pt/C) layers, and a PEM, typically a perfluorosulfonic acid (PFSA) polymer such as Nafion ® . It is, in fact, a superb example of a catalytic membrane reactor performing a variety of reactions and separations. The MEA nanostructure has evolved over a considerable period of time to now provide exceptional performance. Thus, many of the fabrication issues for attaining superior performance have been resolved. However, before wide-spread us- age of PEM fuel cells becomes a reality, there are still a number of technical/cost challenges that remain to be addressed. A key limitation is that the proton conductivity of the PEM is strongly dependent upon its water content, 0920-5861/01/$ – see front matter © 2001 Published by Elsevier Science B.V. PII:S0920-5861(01)00278-4