Synthesis and activity of cobalt-doped barium cerium zirconate for catalysis and proton conduction

Reforming high energy-density liquid fuels in the presence of a catalyst is a convenient means of generating hydrogen for energy conversion in fuel cells, which is always accompanied with several other by-products detrimental to the cell and the environment. For this reason, it is of particular interest to couple the fuel reforming and the hydrogen purification step together. A promising strategy for accomplishing this end is to utilize mixed ionic/electronic conducting ceramics with catalytic functionality and proton conductivity. Cobalt-doped barium cerate and zirconate perovskites (BaCe 1-α-β-γZrβCoγO3-x) display both of these properties. Oxalate chemistry has been used to produce Co-doped powders at low (near ambient) temperatures starting with the nitrate salts of the chosen metals as the precursors. The structure and chemistry of the powder has been monitored at each stage of the preparation using XRD and TEM. The as-precipitated powder is amorphous and crystalline barium cerate, barium zirconate, barium cobaltate are all formed initially after moderate temperature heat treatments. The desired barium cerium zirconate phase with homogeneous Co distribution forms as a result of reaction at high temperatures.