Isotope engineering achieved by local coordination design in Ti-Pd co-doped ZrCo-based alloys

Deuterium/Tritium (D/T) handling in defined proportions are pivotal to maintain steady-state operation for fusion reactors. However, the hydrogen isotope effect in metal-hydrogen systems always disturbs precise D/T ratio control. Here, we reveal the dominance of kinetic isotope effect during desorption. To reconcile the thermodynamic stability and isotope effect, we demonstrate a quantitative indicator of T_gap and further a local coordination design strategy that comprises thermodynamic destabilization with vibration enhancement of interstitial isotopes for isotope engineering. Based on theoretical screening analysis, an optimized Ti-Pd co-doped Zr_0.8Ti_0.2Co_0.8Pd_0.2 alloy is designed and prepared. Compared to ZrCo alloy, the optimal alloy enables consistent isotope delivery together with a three-fold lower T_gap, a five-fold lower energy barrier difference, a one-third lower isotopic composition deviation during desorption and an over two-fold higher cycling capacity. This work provides insights into the interaction between alloy and hydrogen isotopes, thus opening up feasible approaches to support high-performance fusion reactors.