Improving dehydrogenation properties of Mg/Nb composite films via tuning Nb distributions

To investigate the effect of Nb on the dehydrogenation properties of Mg–Nb composite films, Mg/Nb eight-layer film and Mg-10 at% Nb alloy film with the similar Mg-to-Nb atomic ratio were prepared by magnetron sputtering. Results show that both Mg/Nb eight-layer film and Mg-10 at% Nb alloy film exhibit excellent de/hydrogenation properties. Mg-10 at% Nb alloy film starts to release hydrogen at 108 °C, and its desorption peak temperature is lower to 146 °C, which is much better than that of pure MgH₂ under the same condition. Scanning electron microscopy (SEM) results demonstrate that the dispersive Nb nanoparticles in Mg/Nb eight-layer film may serve as nucleation sites for Mg ↔ MgH₂ reactions, which can provide channels for H diffusion. For Mg-10 at% Nb alloy film, the uniform distributions of Nb can accelerate the hydrogen diffusion and effectively improve the dehydrogenation kinetics for MgH₂. This study provides an enlightening way for designing and preparing Mg-based composite films with excellent dehydrogenation properties.