Fuel Cell Technology: Reaching Towards Commercialization

Chapter 2: PEM Fuel Cells

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2.1 Introduction

PEM fuel cells use a proton conductive polymer membrane as electrolyte. PEM stands for Polymer Electrolyte Membrane or Proton Exchange Membrane. Sometimes they are also called polymer membrane fuel cells, or just membrane fuel cells. In the early days (1960s) they were known as Solid Polymer Electrolyte (SPE) fuel cells. This technology has drawn the most attention because of its simplicity, viability, quick start-up, and it has been demonstrated in almost any conceivable application, from powering a cell phone to a locomotive.

At the heart of a PEM fuel cell is a polymer membrane that has some unique capabilities. It is impermeable to gases but it conducts protons (hence Proton Exchange Membrane name). The membrane, which acts as the electrolyte, is squeezed between the two porous, electrically conductive electrodes. These electrodes are typically made out of carbon cloth or carbon fiber paper. At the interface between the porous electrode and the polymer membrane there is a layer with catalyst particles, typically platinum supported on carbon. A schematic diagram of cell configuration and basic operating principles is shown in Figure 2.1 [1], [2].


Figure 2.1: The basic principle of operation of a PEM fuel cell [1], [2]

Electrochemical reactions occur at the surface of the catalyst at the interface between the electrolyte and the membrane. Hydrogen, which is fed on one side of the membrane, splits into its primary constituents protons and electrons. Each hydrogen atom consists of one electron and one proton. Protons travel...

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