In situ high temperature X-ray diffraction studies of mixed ionic and electronic conducting perovskite-type membranes

Phase structure and stability of three typical mixed ionic and electronic conducting perovskite-type membranes, SrCo0.8Fe0.2O3-delta (SCF), Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and BaCo0.4Fe0.4Zr0.2O3-delta (BCFZ) were studied by in situ high temperature X-ray diffraction at temperatures from 303 to 1273 K and under different atmospheres (air, 2% O-2 in Ar and pure Ar) at 1173 K. By analyzing their lattice parameters the thermal expansion coefficients (TECs) of BSCF, SCF and BCZF are obtained to be 11.5 x 10(-6) K-1, 17.9 x 10(-6) K-1 and 10.3 x 10(-6) K-1, respectively. A relationship between phase stability and TEC was proposed: the higher is the TEC, the lower is the operation stability of the perovskite materials. (C) 2005 Elsevier B.V. All rights reserved.

Stainless-steel-net-supported zeolite NaA membrane with high permeance and high permselectivity for oxygen over nitrogen

A stainless-steel net is used to support a zeolite NaA membrane synthesized using a 'seeded-growth' method. The zeolite and stainless-steel net are tightly integrated (see Figure), showing large-scale order and high mechanical stability. High oxygen permeance and high permselectivity for O-2 over N-2 (about 7) is demonstrated.

Benzene electro-oxidation in a PEMFC for phenol and electricity cogeneration

In the present investigation, the electrochemically-assisted oxidation of benzene in a H-2-O-2 proton exchange membrane fuel cell (PEMFC) for electricity and phenol cogeneration is studied. Experiments were carried out in a PEMFC electrochemical reactor using Pd black as cathode electrocatalyst at 60 and 80 degrees C, respectively and 1 atm back pressure. Indeed, it was found that the only product detected under the examined experimental conditions was phenol. The online GC product analysis revealed that it is impossible to produce phenol when the fuel cell circuit is open (I = 0) under all the examined experimental conditions. When the fuel cell circuit was closed, however, the phenol yield was found to follow a volcano-type dependence on the cur-rent of the external circuit. It was found that the maximum phenol yield was 0.35% at 100 mA/cm(2) at 80 degrees C. At the same time, the PEMFC performance was also investigated during the phenol generation process. Furthermore, experiments with the rotating ring disc electrode (RRDE) technique showed that the intermediate oxidation product, i.e. H2O2 existed during the oxygen electro-reduction process. The cyclic voltammograms showed that benzene was strongly adsorbed on the Pd surface, leading to a degradation of the PEMFC performance. (c) 2005 Elsevier B.V. All rights reserved.