Effect of Nb on hydrogen storage properties of Ti–V–Cr-based alloys

This research investigates the impact of incorporating Nb into Ti–V–Cr-based alloys, with compositions ranging from Ti 30-x V 35 Cr 35 Nb x (x = 0, 5, 10, 15, and 20 at. %), with the objective of enhancing hydrogen storage properties. Employing a comprehensive approach encompassing design, synthesis, and characterization, the study aimed to develop novel hydrogen storage alloys . Utilizing the CALPHAD method, the alloys were designed to anticipate the formation of multicomponent single-phase structures. Structural and microstructural analyses of the synthesized alloys were conducted using XRD , SEM , and EDS techniques. The hydrogen storage capabilities were evaluated utilizing a Sieverts’ type apparatus. The investigated alloys displayed a singular-phase BCC solid solution , characterized by dendritic microstructures. Notably, the Nb-free alloy, Ti 30 V 35 Cr 35 , demonstrated the highest hydrogen storage capacity, reaching 3.62 wt% (∼1.9 H/M) under 20 bar of H2 at room temperature. Among the Nb-containing alloys, Ti 25 V 35 Cr 35 Nb 5 exhibited a capacity of 2.91 wt% (∼1.6 H/M) under identical conditions. Furthermore, the incorporation of Nb up to 10 at. % effectively bolstered cycle durability. This study underscores the presence of an optimal Nb content crucial for achieving the highest hydrogen capacity and cycle durability in these alloys. • Alloys of the Ti–V–Cr–Nb system for hydrogen storage were designed by CALPHAD calculations and produced by arc melting. • Maximum hydrogen storage capacity of the Nb-free alloy reaches 3.6 wt%; while that containing 5 at. % Nb is 2.91 wt%. • The hydrogen storage behavior requires a two-step phase transformation process (BCC.→BCT monohydride→ FCC dihydride). • Cycle durability improves in the alloy with 10 at. % Nb, but higher Nb content reduces hydrogen storage capacity.