Hydrogen permeation and chemical stability of Ni–BaCe0.7In0.2Ta0.1O3−δ cermet membrane

Abstract

With its good mechanical strength, high hydrogen permeability, and low price, the dense metal ceramic hydrogen separation membrane has attracted increasing attention. The conductivity of perovskite–type proton conductors can be greatly improved by rare–earth doping. In this study, a new nickel/barium cerate cermet Ni–BaCe0.7In0.2Ta0.1O3–δ electron–proton mixed conducting membrane was prepared and its hydrogen permeability, proton conductivity, and chemical stability were tested. Hydrogen permeability was controlled by the bulk diffusion when the thickness was >0.8 mm, but controlled by both the surface exchange and the bulk diffusion when the thickness was <0.8 mm. Ni paste and Pt paste were coated on the surface of the membrane to a thickness of 0.6 mm. After surface modification with the Pt and Ni, the hydrogen permeability of the membrane surface was greatly improved compared with that of the unmodified membrane, owing to better hydrogen catalytic performance of Pt than Ni. Under different CO2 concentrations, the hydrogen penetration flux quickly decreased and then remained nearly stable. The degree of reduction increases with the carbon dioxide concentration increasing. When the CO2 was turned off, the hydrogen permeation rate was restored, and recyclability decreased with increasing CO2 concentration. The changes in phase composition and microtopography implied the reaction between the sample and the CO2. Therefore, these results showed that hydrogen permeability was further improved, not only by reducing the membrane thickness, but also by catalyzing the membrane surface.