The surface coverage of PEM fuel cell electrodes

A quantitative study was conducted about Hydrogen (H2), water (H2O) and carbon monoxide (CO) bond concentration on a Pt-Ru catalyst surface used for PEM fuel cells. Strong hydrogen bonds which can withstand CO exposure at 50 °C were calculated as 54% of the total hydrogen bonds present on catalyst surface during pure H2 purge. The very weak hydrogen bonds that could be removed with pure inert gasses were not taken into account. Additionally, water and hydrogen content on the surface of catalyst layer was compared and hydrogen bond ratios of 33 – 63 % were obtained for different temperatures (25 °C, 50 °C and 75 °C) and relative humidity values (Dew Point Temperatures of 25 °C, 35 °C and 45 °C). Furthermore 10 ppm CO exposure time was varied from 30 second to 1 hour at 50 °C. Majority of the weak hydrogen bonds desorbed in first 10 minutes with 300 sccm gas flow over 9.5 cm2 Pt-Ru catalyst layer. Desorption process stopped after 10 minutes. The hydrogen bonds were strong enough to stick to the surface during 10 ppm CO exposure at 50 °C. Hydrogen bond content ratio of 66-67 % was calculated for 10 – 60 minutes of 10 ppm CO exposure.JRC.F.2-Energy Conversion and Storage Technologie