Chapter 12 - Electrochemical Half-Cells for Evaluating PEM Fuel Cell Catalysts and Catalyst Layers

Abstract

As described in Chapter 1 , the electrochemical reactions in a proton exchange membrane fuel cell include two half-cell reactions: the fuel oxidation reaction, such as the hydrogen oxidation reaction (HOR), occurs at the anode while the oxygen reduction reaction (ORR) proceeds at the cathode. When investigating one reaction and its associated catalysis mechanism, as well as the effects that operating conditions have on this reaction, possible interference from the other reaction is normally eliminated through a half-cell method. In addition, for quick downselection of electrode materials and components, such as the catalyst and its associated catalyst layer, an ex situ approach using a half-cell setup is the quickest and most cost-effective method. Half-cell testing is usually conducted in a three-electrode system containing working, counterelectrode and reference electrodes. Cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode, and electrochemical impedance spectroscopy are the typical half-cell testing techniques to investigate a catalyst’s characteristics in terms of the HOR and ORR. Besides their utility for investigating these two reactions, some special half-cell designs also allow testing of other operating conditions, such as catalyst layer/membrane electrode assembly designs, temperature, pressure, humidity, as well as fuel and air-flow rates.