The compounds La 2 - x Sr x NiO 4 + δ , x=0, 0.1, have been prepared with an oxygen excess of up to δ=0.24. The oxygen tracer diffusion coefficient and surface exchange coefficient of the materials have been determined by the isotope exchange depth profile method (IEDP). La 2 NiO 4 + δ was found to have an oxygen diffusivity higher than that of La 0 . 6 Sr 0 . 4 Co 0 . 2 Fe 0 . 8 O 3 (LSCF) and one order of magnitude lower than the best perovskite oxide ion conductor La 0 . 3 Sr 0 . 7 CoO 3 (LSC). The fast oxide ion diffusion of La 2 NiO 4 + δ combined with its thermal stability indicate that this material would be a good candidate for use in ceramic oxygen generators (COGs) and solid oxide fuel cells (SOFCs). Furthermore, optimisation by a combination of donor and/or acceptor doping should improve the properties reported here.