Cell voltage Ceramic materials

The results for using ceramic materials as an integral component for micro fuel cells have conclusive evidence that ceramics make an excellent separator plate for micro fuel cells. The thin structure of ceramics allows for rigidity without sacrificing increased resistance. A lower contact resistance when compared to other common separator materials increases power output. Ceramic s inert composition also provides excellent reliability in acidic conditions of the fuel cell. Ceramic separator plates achieved the highest power density of comparable materials and subsequently produced less than 10% voltage variation over 1,000 h of testing. 

Figure I.6a also reveals the timeline of milestones in fuel cell design. The leftmost curve is the performance curve of the first practical H2/O2 fuel cell, built by Mond and Langer in 1889 (Mond and Langer, 1889). The electrodes consisted of thin porous leafs of Pt covered with Pt black particles with sizes of 0.1 lam. The electrol)de was a porous ceramic material, earthenware, that was soaked in sulfuric acid. The Pt loading was 2 mg cm and the current density achieved was about 0.02 A cm at a fuel cell voltage of 0.6 V. The next curve in Figure I.6a marks the birth of the PEFC, conceived by Grubb and Niedrach (Grubb and Niedrach, 1960). In this cell, a sulfonated cross-linked polystyrene membrane served as gas separator and proton conductor. However, the proton conductivity of the polystyrene PEM was too low and the membrane lifetime was too short for a wider use of this cell. It needed the invention of a new class of polymer electrolytes in the form of Nafion PFSA-type PEMs to overcome these limitations.

Amperometric sensing of gases is based on solid ion-conducting materials, as described for potentiometric gas sensors. Solid-state amperometric gas sensors measure the limiting current (ij) flowing across the electrochemical cell upon application of a fixed voltage so that the rate of electrode reaction is controlled by the gas transport across the cell. The diffusion barrier consists of small-hole porous ceramics. The limiting current satisfies the relationship ... 

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