Study of the enhanced hydrogen storage of NaAlH₄ by synergistic effects of nanoconfinement and nitrogen doping

Abstract

Considering energy shortage and climate change, the demand for hydrogen as a new energy carrier has increased. The key challenge in the hydrogen energy system is safe and efficient hydrogen storage methods. Complex hydride such as $NaAlH_4$ is a fascinating candidate due to its high storage capacity. However, thermodynamic and kinetic barriers of complex hydride induce high-temperature conditions with low reversibility. To deal with such issues, the size of complex hydrides is reduced by confinement, or hetero-elements are doped to complex hydride, expecting enhanced storage properties through a shortened diffusion path, thermodynamically altered pathway, and catalytic effects. In our system, to optimize hydrogen sorption kinetics and thermodynamics, $NaAlH_4$ is nanoconfined into the nitrogen-doped porous carbon structure. The synergistic effects of nanosized $NaAlH_4$ and charge transfer from nitrogen provide the lowest activation energy for the dehydrogenation of $NaAlH_4$ composite. This strategy can be accommodated into other hydride-scaffold systems for overcoming practical barriers.