Hydrogen Spillover Enhanced Hydriding Kinetics of Palladium-Doped Lithium Nitride to Lithium Imide

Hydrogen storage in complex metal hydrides often suffers from unsatisfied hydriding kinetics of the corresponding complex metals under moderated conditions, partly due to the kinetic barrier associated with the breaking of the H−H bond. Therefore, doping catalysts for H−H bond breakage become a feasible strategy to improve the hydriding kinetics because hydrogen adatoms can efficiently spill over from catalyst to complex metals. To realize this strategy, we developed a unique method to uniformly dope catalytic metal in the storage complex metals via synthesis of the eutectic of the catalytic metal and the precursory storage metal. This method eliminates the use of support materials for catalysts, while still maintaining the large surface area and uniformity of the catalysts. We demonstrated that Li 3 NPd 0.03 with nanoscopic Pd uniformity can be prepared through nitridization of LiPd 0.01 eutectic. The resulting Li 3 NPd 0.03 exhibits enhanced hydriding kinetics over pure Li 3 N for the reaction Li 3 N + H 2 ↔ Li 2 NH + LiH under moderate conditions. The activation barrier for the hydriding of Li 3 NPd 0.03 was measured to be ∼28 kJ/mol. DFT calculation reveals that the hydrogen adatom migration barrier from the palladium to the nitrogen atom is ∼25 kJ/mol. These results indicate that the Pd-doped LiN 3 is hydrided by hydrogen adatoms that migrate from the Pd catalyst and the kinetic barrier for such a hydriding process is mainly ascribed to the diffusion barrier of the H adatom from the palladium to the nitrogen atom.