(504f) Electrical Conductivity and Chemical Stability of Novel Titanium-Doped Mixed Proton- and Electron-Conducting Perovskite Membranes for Pure Hydrogen Production
Mixed proton- and electron-conducting membranes (MPECMs) are highly promising for hydrogen separation because of elevated operation temperature in excess of 1073K, theoretically infinite hydrogen permselectivity and lower cost as compared to noble-metal membranes. The unique combination of these characteristics makes them highly attractive for in-situ hydrogen separation from products of such high temperature reactions as partial oxidation of methane and coal gasification. However, the hydrogen permeability of current MPECMs is relatively low and their chemical stability under carbon dioxide atmosphere is rather poor. In the present study, we investigated the effect of Ti doping on phase structure, thermal and chemical stability, electrical conductivity, and hydrogen permeation properties of Yb, Tm-substituted SrCeO3 perovskite MPECMs. The structure of these doped perovskites was characterized by XRD and their stability in various gas environments by TGA-DSC and in-situ high temperature XRD. The doped perovskites preserved pure perovskite structure under experimental conditions investigated in this study. The weight increase of Ti-doped perovskites after exposure to pure carbon dioxide atmosphere at 1173 K with pressure of 1 atm was significantly smaller than that observed in the case of the typical SrCe0.95Yb0.05O3 perovskite (~13%). The morphology of Ti-doped perovskites and corresponding membranes was characterized by SEM. Best Ti-doped membranes containing a pure perovskite phase and displaying good stability and high density were chosen for further characterization of electrical conductivity in different gas environments. These experimental results demonstrated that our Ti-doped perovskites are highly promising materials for hydrogen separation membranes with high hydrogen permeability and good chemical stability above 1073 K.