Solid-State Electrolytes and Electrode Materials for Fuel Cell Application

Abstract

Depending on the temperature of operation, there are two major types of fuel cells based on solid-state electrolytes, namely (a) solid oxide fuel cells with an operating temperature of 500–1000 °C, (b) polymer electrolyte membrane fuel cells with an operating temperature in the range 60–200 °C. For the first category, primary focus is given on the development of conventional 8 mol% yttria-stabilized zirconia (8-YSZ)-based materials along with the addition of transitional metal ion dopants that reduce the sintering temperature of the 8-YSZ making fabrication of the cells easier. Possibility of using doped ceria-based electrolyte has also been discussed briefly. Various solid-state electrodes, especially the Sr-doped lanthanum manganite, Sr-doped lanthanum ferrite, Sr-doped lanthanum cobaltite and Sr- and Co-doped barium ferrite, etc., have been reviewed both in terms of general characteristic and also the developmental activities taken up in the authors’ laboratory. Similarly, solid-state anode materials, e.g. Ni–YSZ, as developed at authors’ laboratory have been critically reviewed with the emphasis on the fabrication of single cell. Functionality in terms of powder synthesis and fabrication of multilayer composite anode have been discussed with electrochemical performance. The cell performance is clinically correlated with the cell microstructure. For the other category, direct alcohol fuel cells (DAFCs) technology has earned a considerable interest as one of the promising electrochemical conversion devices. However, the challenges in DAFCs arise from the need for inexpensive and durable electrocatalyst. In this regard, nanostructured Pt or Pd metal-based electrocatalysts hold the key to its advances. Nanoclusters, nanowire and nanotubes of these noble metals or their alloys have been used extensively. Some of the recent research efforts towards development of both cathode and anode electrocatalysts along with their advantages and disadvantages for low-temperature fuel cell application are highlighted.