Polymer Electrolyte Membrane Fuel Cells

2. Electrodes

Ceramic Carbon Electrodes For Fuel Cell Systems

Conventional fuel cell electrodes are composed of Pt supported on carbon that is mixed with the Nafion, a proton conducting ionomer. Nafion serves to increase proton conductivity within the catalyst layer which improves catalyst utilization. However, excess Nafion is detrimental to fuel cell performance since it restricts gas flow.

Ceramic carbon electrodes (CCEs) are promising alternatives to Nafion-based electrodes due to their high surface area and durability.  CCEs consist of electronically conductive carbon particles bound with a ceramic binder via the sol-gel process.  One key advantage of this method of electrode fabrication is that the ionomer is added to the catalyst layer in monomer form and subsequently polymerized in the presence of electrocatalyst. Thus, a structure can be formed where the ionomer is intertwined with the catalyst particles at the nanoscale, which should lead to maximum catalyst utilization. The adjacent figure shows (a) a photograph (b) a schematic representation and (c) a FEG-SEM image of a CCE catalyst layer.

Our research has shown that CCEs do have the potential to replace traditional fuel cell electrodes.  We have developed a proprietary method for the development of ceramic carbon electrodes, which deliver superior functional characteristics to Nafion.  It is well documented that the performance of Nafion-based systems decrease greatly when the cathode gas feed relative humidity (RH) is low.  The novel Ceramic Carbon Electrode (CCE) material experiences no change in cell performance when the cathode gas feed is decreased, all the way down to 20% RH.  Further, our CCE achieves similar performance to Nafion at 100%RH.  As a result, the technology reduces the requirement for humidification and therefore water control systems in vehicle manufacture, while also decreasing the possibility of PEM cell flooding. Currently, we are investigating materials based upon other sulfonated silicate ionomers and comparing electrochemical results to those of Nafion, as well as determining optimal conditions for their use in fuel cell systems.  

More details on our research in this area can be found in the following publications:

  1. J. I Eastcott, E. B. Easton, "Sulfonated Silica-Based Fuel Cell Electrode Structures for Low Humidity Applications", J. Power Sources, 245 (2014) 487 – 494.  doi: 10.1016/j.jpowsour.2013.07.005 
  2. J.I. Eastcott, E.B. Easton, "Electrochemical Studies of Ceramic Carbon Electrodes for Fuel Cell Systems: A Catalyst Layer Without Sulfonic Acid Groups", Electrochim. Acta, 54, 3460-3466 (2009). doi:10.1016/j.electacta.2009.01.007

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