CO-tolerant operation of platinum-loaded PEM fuel cells

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.