Development of passive hydrogen separation membranes made from Co-synthesized nanoscale cermet powders

A powder comprised of nickel oxide and proton-conducting Nd- and Zr-doped barium cerate with a particle size on the order of 10 nm has been co-synthesized using the glycine–nitrate combustion process. The two compositions are intimately mixed with no significant elemental substitution between them after synthesis. To ensure complete reaction of the cerate components, the synthesized powder must be calcined at 1000∘C. Among the barium cerate compositions investigated, the 30% Zr- and 15% Nd-doped material exhibited the best combination of chemical stability in CO2 and conductivity in hydrogen environments. At least 35 vol% Ni is required to achieve percolation in the composites. When sintering is carried out in an atmosphere which promotes reduction of nickel oxide to nickel metal, the result is a mixed electronic- and protonic-conducting composite which has potential use as a hydrogen separation membrane. Composites with a relative density of 99.2% and nanoscale grains have been prepared by hot pressing.