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.