CO-tolerant operation of platinum-loaded PEM fuel cells

Abstract

Abstract-Biomass is a green energy source, which can be converted to hydrogen rich gas. If this gas is used as feedstock for a PEM fuel cell, it is possible to convert biomass to electricity in an environmental friendly way. A disadvantage of a PEM fuel cell is that platinum, which is used as catalyst to speed up the anode reaction, is a good adsorbent for CO. Carbon monoxide will adhere to the platinum surface blocking the catalyst for hydrogen oxidation. In order to clean the catalyst, oxygen can be added to the fuel stream. By applying negative voltage pulses to the cell terminals, existing water can get electrolyzed. This results in trace amounts of oxygen in the anode channel.Measurements performed on a poisoned fuel cell stack have been conducted. The results of the measurements show that the poisoned cells regenerate after a negative pulse. By optimizing the pulse amplitude, repetition time and duty cycle, the fuel cell used is CO-tolerant for gasses containing 50 ppm CO. Furthermore, cell oscillations, probably related to self-oxidation of carbon monoxide, are observed, which is remarkable for PEM fuel cells with pure platinum loaded catalysts.

Carbon monoxide poisoning and mitigation strategies for polymer electrolyte membrane fuel cells – A review

“…The electrical position of the individual cells in the stack determined their CO-tolerance and regeneration. 197 Other advantages found by Mao et al (2000) were the rapid and more controllable application of this pulsing technique compared to oxidant bleeding. 198…”

“…Wingelaar et al (2007) studied the application of periodic negative voltages to regenerate a system composed of four cells fed in series, but electrically connected in pairs (the first two and the last two in parallel). 197 Although the application of negative voltage pulses requires a significant amount of power, it was possible to increase to up to 500% the voltage output of the system when exposed to 50 ppm CO/H2. The electrical position of the individual cells in the stack determined their CO-tolerance and regeneration.…”

Development of a power converter to improve CO tolerance in proton exchange membrane fuel cells

“…A drawback of this method is that the produced fuel is not pure and contains by-products of the process such as carbon monoxide (CO), which can be as high as 500 ppm during reformer starting process. This poses an additional issue to the operation of PEM stacks, since it has been shown that the use of CO contaminated fuel degrades the performance of the fuel cell in terms of output voltage and power due to poisoning of the platinum catalyst contained in its membrane [7,8].…”