Ta–W metal alloy membrane reactor for HI decomposition in I–S thermochemical cycle for hydrogen production

Abstract

HIx processing section of Iodine-Sulfur (IS) thermochemical cycle suffers from the drawbacks of highly corrosive environment and a low thermodynamic conversion of HI decomposition (∼22% at 450 °C). This study investigates, for the first time, the potential of tantalum-tungsten (Ta–W) metal alloy membrane reactor for the decomposition of HI. A thin film of Ta–W alloy was deposited on clay-alumina support by DC magnetron sputtering under optimized set of parameters. The corrosion resistance of the Ta–W membrane was evaluated through electrochemical corrosion studies and immersion coupon tests in azeotropic HI (57 wt % in water) environment. The results confirmed that Ta–W had a higher corrosion resistance than Ta. HI decomposition was carried out in Ta–W membrane reactor and suitable operating parameters were finalized. An enhanced conversion of ∼98% was obtained at 450 °C and 105 Pa, while no permeation of HI, water and iodine was observed across the membrane.