2LiBH-MgH System Catalytically Modified with a 2D TiNbO Nanoflake for High-Capacity, Fast-Response, and Long-Life Hydrogen Energy Storage.

To achieve large-scale hydrogen storage for growing high energy density and long-life demands in end application, the 2LiBH-MgH (LMBH) reactive hydride system attracts huge interest owing to its high hydrogen capacity and thermodynamically favorable reversibility. The sluggish dehydrogenation kinetics and unsatisfactory cycle life, however, remain two challenges. Herein, a bimetallic titanium-niobium oxide with a two-dimensional nanoflake structure (2D TiNbO) is selected elaborately as an active precursor that transforms into TiB and NbB with ultrafine size and good dispersion in the LMBH system as highly efficient catalysts, giving rise to excellent kinetic properties with long-term cycling stability. For the LMBH system added with 5 wt% 2D TiNbO, 9.8 wt% H can be released within 20 min at 400 °C, after which the system can be fully hydrogenated in less than 5 min at 350 °C and 10 MPa H. Moreover, a dehydrogenation capacity of 9.4 wt% can be maintained after 50 cycles corresponding to a retention of 96%, being the highest reported to date. The positive roles of TiB and NbB for kinetics and recyclability are from their catalytic nucleation effects for MgB, a main dehydrogenation phase of LMBH, thus reducing the apparent activation energy, suppressing the formation of thermostable LiBH byproducts, and inhibiting the hydride coarsening. This work develops an advanced LMBH system, bringing hope for high-capacity, fast-response, and long-life hydrogen energy storage.