1 Plasma Activated Fuel Cells

Plasma-activated fuel cell operation is examined using dielectric-barrier discharges introduced into the inlet fuel and air streams of laboratory proton exchange membrane (PEM) based devices. We compare the performance of the hydrogen-driven-PEM fuel cell in the presence/absence of the plasma discharge, and under conditions of three different types of membrane electrode assemblies (MEAs). The results of these studies indicate that a conventional Nafion membrane with a catalyst and carbon cloth gas diffusion layer (GDL) show little enhancement under plasma exposure. Removal of just the GDL was also unaffected by the discharge activation, however, operation of the fuel cell with a bare Nafion membrane resulted in an open circuit voltage (OCV) of 1.8V, a nearly 1V increase over the OCV obtained in the standard configuration. No attempt has yet been made to analyze the current-voltage characteristic, as the current is presently limited by the ability to draw away surface charge. The results are nevertheless encouraging, and ongoing studies include the development of a suitable carbon layer to serve as an electrode while providing adequate exposure of the membrane to the adjacent plasma. In parallel, we have developed models of the plasma activated streams, for use in simulating in-situ methane reforming of hydrogen. Experiments are underway in measuring the OCV when operating on methane and dilute methane fuel streams. Introduction This research involves the study of the use of non-equilibrium plasma discharges generated in-situ, within the inlet channels of fuel cells, to enhance fuel cell efficiency. While in theory, a fuel cell can have a potentially high thermodynamic efficiency (~ 80 % for a proton exchange membrane (PEM) fuel cell at 100 °C and 1 atm pressure), in practice, fuel cells exhibits a much lower efficiency (~ 40 %) due to three major factorsactivation, ohmic and mass transport losses. The activation loss is caused by the inefficiencies at which reactants form ions and electrons at the catalyst surface. Ohmic loss is due to finite ion diffusion rates through an electrolyte. The mass transport loss is primarily a result of the limited rate of ion flux in the gas diffusion layer (GDL). Here, we believe that the use of a non-equilibrium plasma discharge can eliminate/diminish those losses for the following reasons; (i) the non-equilibrium plasma can generate high ion/atom/radical concentrations in low power/volume requirements, which can reduce the activation loss (or may eliminate the need for the catalyst layer altogether), (ii) the presence of higher concentrations of ion/atoms/radicals in the flow channel should partially alleviate the concentration limit caused by the saturation of mass transport, (iii) the dissociation and the activation of reactants before the GDL due to the presence of the non-equilibrium plasma may improve the diffusion characteristic of the species through the layer. The exploratory phase of this research is aimed at: (a) carrying out a system level analysis to determine the overall benefits that a plasma discharge can offer to fuel cell systems; (b) designing a preliminary laboratory-scale fuel cell/plasma discharge assembly;