Hydrogen storage in the format of complex metal hydrides often suffers from unsatisfied hydriding kinetics of the initial metal complex under moderated conditions, partly due to the kinetic barrier associated with the breaking of H-H bond. We show that by doping nanocatalysts for H-H bond breakage is a feasible way to improve the hydriding kinetics of metal complex. Instead of using the traditional supported heterogeneous catalyst, we developed a unique method to uniformly dope catalytic metal directly in the storage metals complex via synthesis of the solid solution of the catalytic metal and the precursory storage metal. This method eliminates the use, thus its weight, of the support materials. We demonstrated that Li3NPd0.03 with nanoscopic Pd uniformity can be prepared through the nitridization of LiPd0.01 solid solution. The resulting Li3NPd0.03 exhibits enhanced hydriding kinetics over pure Li3N for reaction Li3N + H2 ? Li2NH + LiH. The activation barrier for the hydriding of Li3NPd0.03 was measured to be ~28 kJ/mol. DFT calculation reveals that the hydrogen adatom migration barrier from palladium to nitrogen atom is ~25 kJ/mol. These results indicate that the Pd-doped LiN3 is hydrided by hydrogen adatom that migrate from the nano Pd, and the kinetic barrier for such a hydriding process is mainly ascribed to the diffusion barrier of H adatom from palladium to nitrogen atom.

Direct doping of Pd nanocatalysts in metal complex for enhanced hydriding kinetics

246th National Meeting (2013)

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