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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.

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Ohmic contacts and Schottky contacts were made on an undoped AlGaN/GaN FET structure. Despite the high Al content (33%), we were still able to obtain a contact resistance of 0.3 ωmm. Pulsed measurements showed the large effect of self-heating even for circular contacts with a radius of 50 μm. The behavior ofthe Ni/Au Schottky contacts is according to the charge control model; the reverse current and capacitanceonly scale with the area of the diode. Tests with polygon type diodes showed no dependence of the reverse current on the number of polygon corners. The reverse current decreased when the devices were aged at 400°C for 30 hrs. Coplanar Waveguide discontinuities were realized on AlN substrates. A scalable lumped element model was derived from measurements for T-junctions, transmission lines, bends and crosses.