Trace Nb and Mn Regulation of Hydrogen Storage Capacity and Cyclic Stability of BCC-Type TiCrMo Alloys

Body-centered cubic (BCC) structured TiCrMo alloys have emerged as an auspicious hydrogen storage material system due to their high hydrogen storage capacity and excellent cost-effectiveness. However, their poor cyclic stability remains a critical bottleneck hindering large-scale applications. In this study, the atomic size difference in the alloy was regulated by trace Nb and Mn to improve hydrogen storage capacity and cyclic stability. The results show that while trace Nb regulation enhances the cyclic stability of the alloy, it comes at the cost of sacrificing part of the hydrogen storage capacity; in contrast, trace Mn regulation exhibits superior comprehensive performance, it maintains a reversible hydrogen storage capacity of nearly 2.5 wt % at 303 K. After 100 cycles, the capacity retention rate increases from 73.44% to 83.55%, significantly improving cyclic stability. Furthermore, mechanistic analysis reveals that the alloy’s capacity degradation stems from the increased disparity in local atomic configurations during cycling, which intensifies hydrogen trapping, thereby impairing the reversibility of phase transformation and ultimately reducing the number of effective hydrogen storage sites. The findings of this study provide a theoretical basis and technical strategies for the development of low-cost, long-cycle-life BCC-type hydrogen storage alloys.