Study on Anti-poisoning Property and Mechanism of Rare Earth Superlattice Hydrogen Storage Alloys
The high cost of high-purity hydrogen necessitates the utilization of low-cost industrial by-product hydrogen as an alternative gas source to reduce hydrogen storage costs. Industrial by-product hydrogen typically contains impurities such as H2S and CO, yet the poisoning mechanisms of these gases on superlattice hydrogen storage alloys during hydrogen absorption/desorption remain poorly understood. This study systematically investigates the poisoning effects and regeneration behavior of La0.65Mg1.32Ca1.03Ni9Y0.17 superlattice hydrogen storage alloy in atmospheres containing 10^-3 H2S and CO. The experimental protocol comprised 10 poisoning cycles followed by 1 regeneration, repeated to total 20 poisoning cycles and 2 pure hydrogen regenerations. Results show that in pure hydrogen, the alloy's hydrogen storage capacity gradually decreases after 22 cycles but is effectively restored after dehydrogenation at 473 K. In the presence of impurity gases, the hydrogen storage capacity retention rates after 10 poisoning cycles with H2S and CO are 3.56% and 2.71%, respectively; after 20 cycles, these decrease to 3.68% and 1.73%, respectively. After dehydrogenation at 473 K, retention rates recover to 40.35% and 98.27%, respectively. This indicates that poisoning severity follows the order CO > H2S, while regeneration difficulty follows H2S > CO. X-ray diffraction analysis reveals that after poisoning, the main phase transforms from AB3 to AB3H, but reverts to AB3 after high-temperature dehydrogenation. X-ray photoelectron spectroscopy shows that after H2S poisoning, CaS and CaSO4 form on the alloy surface, indicating irreversible chemical adsorption. In contrast, after CO poisoning, no new substances are detected, indicating reversible adsorption. This study clarifies the differentiated poisoning mechanisms of impurity gases and provides theoretical support for the application of rare-earth superlattice hydrogen storage alloys in complex atmospheres.