Coupled transport membranes utilize the flux of one species to help drive the flux of another species, in some cases even against its own chemical potential gradient. To date, however, coupled transport membrane studies and applications have been almost exclusively confined to aqueous or liquid membrane media. To alleviate the drawbacks to membranes using these materials, we have developed a solid-state coupled transport membrane system based on a proton conducting perovskite ceramic. Using coupled transport effects, this membrane is capable of simultaneously transporting water and oxygen, including the uphill transport of either chemical species. This is the first known example of a solid-state coupled transport membrane and is the first of any type to operate at high temperatures. The unique features of this system open up the possibility of new membrane separation applications, including air separation or natural gas reforming using waste steam and heat streams. (C) 2011 Elsevier B.V. All rights reserved.