Ni-SrCe0.8Yb0.2O3-delta cermet membranes are being developed to separate hydrogen from hydrogen-containing gas mixtures at high temperature. The hydrogen flux of an annealed membrane showed higher flux than that of an as-sintered membrane. The major contribution to overall flux was from ambipolar diffusion through the metal-to-oxide grain boundary. The higher hydrogen permeation flux of an annealed membrane may be understood by its larger metal grains and lower tortuosity, leading to a less-effective length for proton diffusion.