Hydrogen permeation through terbium doped strontium cerate membranes enabled by presence of reducing gas in the downstream

Abstract

Hydrogen permeation through SrCe 1− x Tb x O 3− δ ( x = 0.025, 0.05 and 0.10) membranes using various gas streams as the sweep was investigated. Hydrogen impermeable SrCe 1− x Tb x O 3− δ membranes with air or inert gas in the downstream become hydrogen permeable when there is a reducing gas, such carbon monoxide or hydrogen, existing in the downstream. The membrane remains hydrogen permeable after the downstream sweep gas is changed from the reducing gas to the inert gas. This phenomenon is explained by the electronic conductivity of the materials. These results further confirm that SrCe 1− x Tb x O 3− δ (0.025 < x < 0.1) is a mixed proton–electron conducting material in a hydrogen containing atmosphere. The activation energy of hydrogen permeation is close to the activation energy of electronic conduction of the materials, confirming that the hydrogen permeation is determined by the electronic conductivity of the material. For SrCe 0.95Tb 0.05O 3− δ , increasing the downstream CO partial pressure from 0.001 to 0.1 atm leads to a small increase in hydrogen flux from 1.4 × 10 −2 to 1.6 × 10 −2 ml/cm 2 min. The hydrogen flux of SrCe 1− x Tb x O 3− δ increases with upstream hydrogen partial pressure.