Processing of yttrium-doped barium zirconate for high proton conductivity

The factors governing the transport properties of yttrium-doped barium zirconate (BYZ) have been explored, with the aim of attaining reproducible proton conductivity in well-densified samples. It was found that a small initial particle size (50–100 nm) and high-temperature sintering (1600 °C) in the presence of excess barium were essential. By this procedure, BaZr0.8Y0.2O3-d with 93% to 99% theoretical density and total (bulk plus grain boundary) conductivity of 7.9 × 10^-3 S/cm at 600 °C [as measured by alternating current (ac) impedance spectroscopy under humidified nitrogen] could be reliably prepared. Samples sintered in the absence of excess barium displayed yttria-like precipitates and a bulk conductivity that was reduced by more than 2 orders of magnitude

Alcohol Fuel Cells at Optimal Temperatures

High-power-density alcohol fuel cells can relieve many of the daunting challenges facing a hydrogen energy economy. Here, such fuel cells are achieved using CsH2PO4 as the electrolyte and integrating into the anode chamber a Cu-ZnO/Al2O3 methanol steam-reforming catalyst. The temperature of operation, ~250°C, is matched both to the optimal value for fuel cell power output and for reforming. Peak power densities using methanol and ethanol were 226 and 100 mW/cm^2, respectively. The high power output (305 mW/cm^2) obtained from reformate fuel containing 1% CO demonstrates the potential of this approach with optimized reforming catalysts and also the tolerance to CO poisoning at these elevated temperatures