CO‐Resistant Al‐Doped AB ₅ ‐Type Hydrogen Storage Alloys

The safe and stable hydrogen storage is a key challenge in the development of hydrogen energy. AB 5 ‐type solid hydrogen storage is considered as a promising method due to its excellent reversible absorption/desorption performance and cycling stability at room temperature. However, AB 5 ‐type hydrogen storage alloys are susceptible to poisoning by highly toxic industrial gases, such as CO. In practical applications, impurity poisoning significantly reduces hydrogen absorption/desorption ability. Previously, it was believed that doping Al element could significantly reduce the strength of CO absorption to achieve CO‐resistant performance. Actually, the first‐principles calculations in this study reveal that Al doping does not significantly reduce CO absorption strength (−2.28 eV compared to −2.08 eV for LaNi 5 ). Instead, Al‐doped LaNi 5 acts as a catalyst to promote the methanation reaction of CO at a high temperature of 125°C. The conversion pathway is CO → HCO → CH → CH 2 → CH 3 → CH 4 , converting the highly toxic CO into the weakly toxic CH 4 and H 2 O, with a capacity retention rate of 92% after 10 cycles. Furthermore, Al doping contributes to lowering the absorption plateau, thereby enhancing the alloy's competitiveness between H 2 and CO absorption (0.40 MPa compared to 1.63 MPa for LaNi 5 ). Thus, the exceptional CO tolerance of Al‐doped AB 5 alloys is underpinned by the synergistic effect of CO methanation at elevated temperatures and reduced hydrogen platform pressure, providing a key mechanism for designing next‐generation hydrogen storage materials that are resistant to industrial impurities.