Enhanced performance of CO poisoned proton exchange membrane fuel cells via triode operation

The effect of triode operation on the performance of CO poisoned PEM fuel cells was investigated. In this mode of operation a third, auxiliary, electrode is introduced in addition to the anode and the cathode. Application of electrolytic current in the auxiliary circuit, comprising the cathode and the auxiliary electrode was found to significantly enhance the time-averaged power output of a state-of-the-art PEMFC unit operating with a 70 ppm CO in H2 atmospheric pressure mixture. Both normal and triode operation were found to lead to self-sustained current and potential oscillations in the fuel cell circuit over wide ranges of external resistive load. The time averaged increase in power output was found to be typically a factor of three higher than the power output in conventional fuel cell operation and up to a factor of 1.32 larger than the power sacrificed in the auxiliary circuit. The mechanism of the enhanced anodic electrocatalysis was investigated via the use of two reference electrodes and the results are discussed together with a possible design for application of the triode concept in stacks.

The use of the triode operation mode via application of an auxiliary potential, Uaux, of −1.9 V between the cathode and the auxiliary electrode leads to very significant enhancement in the performance of the CO poisoned PEMFC. The triode operation increases very significantly the region of self-sustained oscillations, indicated by arrows in the figure, and leads to a threefold increase in the time-averaged fuel cell power output. This increase in power output is a factor of 1.32 larger than the power sacrificed in the auxiliary circuit.Figure optionsDownload as PowerPoint slideHighlights
► The triode performance of CO poisoned PEM fuel cells was investigated.
► Triode operation leads to a threefold increase in power output of the fuel cell circuit.
► This increase exceeds by up to a factor of 1.32 the power sacrificed in the auxiliary circuit.
► The effect is mainly due to a significant decrease in anodic overpotential.
► All electrode potentials were monitored via two reference electrodes.