Enhanced hydrogen desorption from Mg(BH₄)₂ by combining nanoconfinement and a Ni catalyst

Magnesium borohydride (Mg(BH₄)₂) has been infiltrated into highly ordered mesoporous carbon (CMK3) containing dispersed Ni nanoparticles (Ni NPs) to investigate the possible synergetic effects of nanoconfinement and catalysis by Ni NPs. Ni NPs (5 wt%) were introduced into the CMK3 nanoscaffold (CMK3-Ni) then Mg(BH₄)₂ was slowly infiltrated into this prepared CMK3-Ni template to synthesize a CMK3-Ni confined (Mg(BH₄)₂) system (denoted as CMK3-Ni-Mg(BH ₄)₂). Solid-state ¹¹B NMR and FT-IR spectra confirmed that Mg(BH₄)₂ was in the pores of CMK3-Ni. Temperature-programmed desorption-mass spectroscopy (TPD-MS) and pressure-composition-temperature (PCT) measurements were utilized to study the hydrogen desorption properties for this nanoconfined CMK3-Ni-Mg(BH ₄)₂ system, which was demonstrated to be remarkably improved, e.g. the hydrogen desorption temperature was dramatically decreased and the release rate was significantly enhanced. The hydrogen started to be released from the CMK3-Ni-Mg(BH₄)₂ at a temperature of only 75 °C (measured by TPD) and reached its peak release rate at a temperature of 155 °C, compared with 270 °C and above 350 °C respectively from pure Mg(BH₄)₂. To the best of our knowledge, this is the first time Mg(BH₄)₂ decomposition has been realized at a temperature below 100 °C, which is of great significance for the use of this material for practical hydrogen storage for proton exchange membrane fuel cells (PEMFCs).