Electrochemical Preferential Oxidizer of Carbon Monoxide in Fuel Cell Reformate

Removal of carbon monoxide from reformate hydrogen providing power to PEM fuel cells

Hydrogen (H2) fueled proton exchange membrane fuel cells (PEMFC) offer an efficient alternative electrical power source for portable appliances. As hydrogen storage is a challenge, recent advances in micro reformer technologies can provide hydrogen from liquid fuels (e.g.: methanol, ethanol). Reformate hydrogen obtained from methanol contains 75% H2, 24% carbon dioxide (CO2) and at least 1% of carbon monoxide (CO). However, studies show CO in reformate hydrogen will affect the PEMFC performance by poisoning the fuel cell’s platinum (Pt) anode. Carbon monoxide concentration in reformate can be minimized via pressure swing adsorption, thermo-catalytic reforming or water gas shift technique, catalytic methanation, or catalytic preferential oxidation with air–bleed. But the volume, weight, power, and fuel efficiency penalties associated with these techniques may constrain their use in certain fuel cell applications.

Electrochemical techniques have previously been explored for the removal of CO from reformate, in which, CO in the reformate hydrogen is adsorbed on a Pt anode, and then, the adsorbed CO is oxidized to CO2 by applying a rectangular pulse potential. For minimizing the hydrogen oxidation loss, Dr. John Weidner has developed a twin cell filter design, in which the two filter cells undergo periodically alternating cycles of CO adsorption and CO oxidation. The time durations of adsorption and oxidation steps are equal for synchronous operation between the two cells. The cathode gas can be either CO free reformate hydrogen exiting the anode compartment or air. Continuous synchronous operation of the filters under ambient conditions with optimum switching times oxidizes most of the CO to CO2 with minimal power