Low-cost iron (Fe) hollow fiber membrane for hydrogen separation

Dense metal membranes are widely studied due to their promising performance in hydrogen separation. In this work, the low-cost dense iron (Fe) hollow fiber membranes (FeHFMs) were developed via the phase inversion and high-temperature sintering method. By tuning the preparation conditions, two typical gas-tight hollow fibers referred to as the sandwich- and honeycomb-structured membranes were successfully synthesized. H₂ permeation behavior was well described by Sieverts equation based on the solution-diffusion mechanism. The sandwich-structured FeHFMs had an H₂ flux of up to 7.51 mmol m⁻² s⁻¹ when operated at a temperature of 850 °C. In comparison, the honeycomb-structured FeHFMs further enhanced the H₂ flux by a factor of 3.2 due to the optimized membrane morphology with only one single dense iron layer. The developed FeHFMs showed superior H₂ permeation stability in thermal shock tests (40 h) and long-term stability tests (120 h). This work also expanded the potential application horizons of the FeHFMs, which can be easily tailored into porous or dense structures by tuning the sintering conditions.