Graphene-supported Pd catalysts for reversible hydrogen storage in LiBH₄

The hydrogen release properties of the graphene supported Pd (Pd-G) catalysts doped LiBH₄ were systematically investigated. It was found that the onset hydrogen desorption temperature of the LiBH₄ doped with 5 wt.% Pd-G-60 (with 60 wt.% Pd loading) catalyst was about 105 C lower than that of the pure LiBH₄ milled under the same conditions, and the other main dehydrogenation peaks of the Pd-G-60 doped LiBH₄ were shifted to 410 and 605 C with an increased total weight loss of 12.6 wt.%. Moreover, the dehydrogenation enthalpy was reduced from 74 kJ mol^-1 H₂ for the pure LiBH₄ to ca. 43 kJ mol^-1 H ₂ for the 15 wt.% Pd-G-60 doped LiBH₄. Importantly, the reversible rehydrogenation process was achieved under 3 MPa H₂ at 400 ^oC for 10 h, and a capacity of ca. 6.6 wt.% was obtained in the 30th cycle, which should be attributed to the evenly dispersed Pd nanoparticles. Meanwhile, LiBH₄ was reformed and one new product, B ₁₆H₂₀, was detected after the rehydrogenation process.