Standard Article

Effect of ionic contaminants

Fuel Cell Technology and Applications

Polymer electrolyte membrane fuel cells and systems (PEMFC)

State-of-the-art performance and durability

  1. T. Okada

Published Online: 15 DEC 2010

DOI: 10.1002/9780470974001.f303054

Handbook of Fuel Cells

Handbook of Fuel Cells

How to Cite

Okada, T. 2010. Effect of ionic contaminants. Handbook of Fuel Cells. .

Author Information

  1. National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan

Publication History

  1. Published Online: 15 DEC 2010

Abstract

In polymer electrolyte membrane (PEM) fuel cells, the electrolyte membrane is easily contaminated by foreign cations because of a higher affinity of these cations with the sulfonic acid group than that of H+. Thereby three modes of degradation in the membrane which affect fuel cell performance are anticipated. The first is a direct effect, and comes from alteration of the membrane bulk properties, e.g., lowering of membrane ionic conductivity, water content, H+ transference number. This effect is normally not so serious unless the membrane is severely contaminated. The second comes from the altered water flux inside the membrane, owing to the terms of electroosmotic drag and diffusion coefficient of water affected by the presence of contaminant ions. This results in membrane drying and lowering of membrane conductivity. The degradation starts when the contaminant level exceeds 5%. Simulation results concerning the water concentration profile, membrane ohmic resistance and membrane overpotential are presented based on water flux equations derived using experimentally obtained transport parameters. The last effect comes from the degradation of the cathode catalyst due to the presence of contaminant ions at the interface between the platinum catalyst and the ionomer layer. This effect is the most serious as regards the fuel cell performance, because a contaminant level as low as 1% is enough to come into effect. Membrane contamination by foreign cations, especially local contamination at the cathode catalyst layer, deteriorates the fuel cell performance significantly, and needs special caution in fuel cell design.

Keywords:

  • cations;
  • cyclic voltammetry;
  • cyclic voltammograms;
  • electrokinetic effects;
  • electroosmotic effects;
  • ionic conductivity;
  • solid-polymer electrolytes (SPE);
  • ionic mobility;
  • overpotential;
  • concentration;
  • oxygen electrode;
  • rotating disk electrode;
  • Koutecky–Levich equation;
  • Nafion®;
  • transport number;
  • transference number;
  • numerical values;
  • water drag coefficient