Adsorption behavior of low concentration carbon monoxide on polymer electrolyte fuel cell anodes for automotive applications

• CO, CO2 and O2 in the anode exhaust were measured during the PEFC operation.
• CO coverage was estimated from gas analysis and CO stripping voltammetry.
• The CO coverage at low CO concentration followed a Temkin-type isotherm.
• The CO coverage was 0.6 at 0.2 ppm CO and 0.11 mg cm−2 anode loading at 60 °C.
• Permeated O2 should have an important role for CO oxidation at low CO concentration.

The adsorption behavior of CO on the anode around the concentration of 0.2 ppm allowed by ISO 14687-2 is investigated in polymer electrolyte fuel cells (PEFCs). CO and CO2 concentrations in the anode exhaust are measured during the operation of a JARI standard single cell at 60 °C cell temperature and 1000 mA cm−2 current density. CO coverage is estimated from the gas analysis and CO stripping voltammetry. The cell voltage decrease as a result of 0.2 ppm CO is 29 mV and the CO coverage is 0.6 at the steady state with 0.11 mg cm−2 of anode platinum loading. The CO coverage as a function of CO concentration approximately follows a Temkin-type isotherm. Oxygen permeated to the anode through a membrane is also measured during fuel cell operation. The exhaust velocity of oxygen from the anode was shown to be much higher than the CO supply velocity. Permeated oxygen should play an important role in CO oxidation under low CO concentration conditions.