High cyclic stability and low plateau of Ti₂V₂Zr/NaH/Al hydrogen storage composite system prepared by ultrasound-assisted ball milling

NaH/Al doped with Ti₂V₂Zr with the aim of lowering the rehydrogenation pressure, lowering the dehydrogenation temperature, and improving the hydrogenation/dehydrogenation kinetics of NaAlH₄. It was found that moderate ultrasonic-assisted wet grinding was beneficial to fine particles efficiently, improved uniformity of particle size, and reduced lattice distortion because its crystalline phase can converge more active hydrogen atoms and reduce the energy barrier of H exchange between the alloy and the matrix, thus improving the comprehensive hydrogen storage performance of the composite systems. It could reversibly store 4.81 wt% of hydrogen and completely hydrogenation under a low hydrogen pressure of 55 atm, its starting and ending dehydrogenation temperatures decrease by 81 and 89 °C, respectively, and the activation energies of the two-step dehydrogenation decrease by 26.7 and 52.7 kJ mol⁻¹ respectively, with a dehydrogenation capacity retention of up to 99.58% over five cycles.