Co@Pd bimetallic catalysts doped on the CNTs for bidirectional improving hydriding/dehydriding property of Mg/MgH2

Mg/MgH2 stands out as an excellent hydrogen storage material due to its abundant presence and its capacity for high hydrogen storage density. However, the sluggish hydrogenation/dehydrogenation kinetics make it unsuitable for solid-state hydrogen storage. To tackle these challenges, the MgH2-Co@Pd-carbon nanotubes composite was created through ball milling, and its hydrogenation/dehydrogenation behavior was examined. The inclusion of Co@Pd notably enhanced the kinetics of hydrogenation/dehydrogenation in Mg/MgH2. The MgCo@Pd-carbon nanotubes composite achieved an absorption of 7.30 wt% H2 in just 8 h of milling. The study proposed an energy conversion model to investigate the enhanced properties of Mg/MgH2. The addition of Co@Pd substantially reduced the activation energy (Ea) for hydrogen desorption to 81.9 kJ/mol. Furthermore, Transmission Electron Microscope and Density Functional Theory simulations were employed to understand how Co@Pd enhances the properties of Mg/MgH2. The improved hydriding/dehydriding kinetics of Mg/MgH2 are likely closely linked to both the confining impact of carbon nanotubes and the synergistic interplay of the "spillover" and "hydrogen pump" effects facilitated by the Co@Pd bimetallic catalysts. The excellent hydriding/ dehydriding behavior is ascribed to the electron spillover and the phase transformation of Mg2Co/Mg2CoH5 and Mg6Pd/Pd. These findings offer new insights into the new insights into the rational design of Co@Pd bimetallic catalysts, which are expected to be an optimal solution for supported catalysts in Mg-based solid-state hydrogen storage systems.