Drew C. Dunwoody, Hachull Chung,

Luke Haverhals, and Johna Leddy[5]

University of Iowa, Department of Chemistry,

Iowa City

CONTENTS

Introduction………………………………………………………………………………………………….. 155

Historical Perspective……………………………………………………………………………………. 157

Catalyst Development………………………………………………………………………. 158

Membrane Development………………………………………………………………….. 159

Thermodynamic Considerations…………………………………………………………………… 160

Thermodynamic Optimum……………………………………………………………….. 160

Realities of Surface Kinetics……………………………………………………………… 161

Performance Targets and Efficiencies………………………………………………………….. 164

General Optimization……………………………………………………………………………………. 166

Electrocatalysts and Supports………………………………………………………………………. 172

Membrane Technology…………………………………………………………………………………. 175

Nafion-Based Membranes……………………………………………………………….. 176

New Separators…………………………………………………………………………………. 178

Closing Thoughts…………………………………………………………………………………………… 182

Abbreviations………………………………………………………………………………………………… 184

References…………………………………………………………………………………………………….. 185

INTRODUCTION

This chapter presents aspects of current developments in direct methanol fuel cell (DMFC) technologies. In particular, the focus is on systems where the fuel stream is a solution of water and methanol fed directly to the fuel cell anode. These systems are the primary focus of the review as cells using reformed methanol as the fuel is a subset of the general class of polymer

electrolyte membrane (PEM) fuel cells that derive hydrogen from reformate sources such as alcohols and hydrocarbons. A diagram of a DMFC is shown in Figure 9.1. A short, historical, retrospective of relevant technologies and the thermodynamics that govern methanol-based fuel cell systems are pre­sented. A survey of the state of the art, largely in terms of performance, are presented for a variety of fuel cell categories. Efficiency and cost are often the driving force behind development efforts. Trends in DMFC design, elec­trocatalyst, and membrane development are discussed. Finally, some closing thoughts and discussion of one of the more challenging limitations of extant DMFC technology. The chapter focuses on the application side of the tech­nology, and, given space constraints, computer modeling studies are not cov­ered in depth. Save for historical references, pains are taken to use the most current references available. The majority range from 2003 to the present.