Different poisoning behaviors of impurity gases on AB2-type Ti-based hydrogen storage alloys and their mechanisms

AB2-type Ti-based hydrogen storage alloys (HSAs) are promising for industrial hydrogen feeding systems due to their moderate operating conditions and high hydrogen storage capacity. However, their practical application is hindered by unavoidable impurity gases in hydrogen feedstocks, which significantly impair the performance of HSAs. Furthermore, the absence of clear evaluation criteria for poisoning behaviors and mechanisms hinders efforts to develop effective mitigation strategies. To address this gap, we used calculated surface interaction energy changes (ΔE) and experimental investigations to classify and rank the poisoning potential of impurity gases on a C14 Laves-phase Ti0.86Zr0.15Mn1.5Cr0.07(VFe)0.43 alloy. Impurity gases were classified into two types of weak-adsorption and strong-adsorption impurity gases by comparing their ΔE with that of H2 ( = −1.6001 eV). As ΔE > , weak-adsorption impurity gases (Ar, He, CH4, and N2) induce poisoning by forming enriched blocking layers that impede H2 diffusion. This blocking effect can be alleviated under gas flow conditions. As ΔE < , strong adsorption gases are further divided into two types based on their reactivity with the alloy. Non-reactive strong-adsorption impurity gases (CO and CO2) preferentially occupy surface active sites, blocking H2 adsorption and dissociation. In contrast, reactive strong-adsorption impurity gases (such as O2) form dense passivation layers that completely prevent hydrogen ingress. Accordingly, surface modification offers an effective approach to mitigate gas-induced poisoning by altering the interaction mechanism. This study establishes the parameter-based criteria for classifying impurity gas poisoning mechanisms in AB2-type Ti-based HSAs. It provides fundamental insights for guiding the design of poisoning-resistant materials and the development of mitigation strategies.