Nanocrystalline Zr_0.8Ti_0.2Co Particles for Hydrogen and H-isotope Storage

ZrCo-based alloys are highly promising solid-state materials for hydrogen isotope storage in controlled nuclear fusion and other related fields. However, their practical application is severely limited by hydrogen-induced disproportionation, which causes rapid performance degradation. While Ti substitution has been shown to reduce disproportionation, the underlying microscopic mechanism, particularly the role of grain boundaries, remains largely unexplored. Here, we combine Ti substitution with a wet-chemical nano crystallization approach to synthesize single nanocrystalline Zr_0.8Ti_0.2Co particles. The material exhibits excellent comprehensive performance, including near-theoretical hydrogen capacity (1.7 wt %), fast room-temperature absorption kinetics (90% of maximum capacity within 20 s), outstanding cyclic stability (93% retention after 50 cycles), and an exceptionally low disproportionation rate (only 2% after 1000 min at 500 °C). First-principles calculations revealed, for the first time, that Ti substitution mitigates hydrogen aggregation at grain boundaries. This effectively blocks the critical initial step of disproportionation, namely hydrogen enrichment at grain boundaries. This work provides a mechanistic perspective on doping-enhanced antidisproportionation through grain boundary stabilization, offering a theoretical foundation for designing next-generation high-performance hydrogen isotope storage materials.