An Investigation On The Hydrogen Desorption Properties And Mechanisms Of LiBH₄Confined/Loaded In Nano-sized Mesoporous Materials

With the development of the society, the demands for clear, environmental friendly and sustainable energy are growing day by day. Due to its higher energy density and zero pollutant, hydrogen has sparked a lot of attention. However, one of the key challenges to realize its commercial application is hydrogen storage. Therefore, it is full of high theoretical significance to explore new high-capacity hydrogen storage materials. With a high storage capacity (18.5wt%) and volumetric hydrogen density (121kg/m3), lithium borohydride (LiBH4) is regarded as one of the most promising hydrogen storage materials. But the slow kinetics, harsh thermal stability and poor reversibility restrict the use of LiBH4. Based on the full overview of the research progress of LiBH4, several LiBH4-based materials were successfully prepared and systematically investigated by varieties of characterization methods. Characterizations such as XRD, SEM, EDS, TEM are used to determine the structure and morphology of the materials. Fourier transform infrared spectroscopy (FTIR) is conducted to verify the presence of LiBH4confined in supporting scaffolds. And the dehydrogenation properties of LiBH4-based materials are characterized by temperature pressure desorption (TPD), pressure-composition-isotherms (PCT), differential Scanning Calorimetry (DSC).(1) Carbon areogels (CA) were fabricated via resorcinol-formaldehyde condensation, and then LiBH4was incorporated into the above aerogel scaffolds. It was found that the nanoconfined LiBH4exhibited good dehydrogenation performances, that is, the lower desorption temperature and the faster desorption rate. The synthesized LiBH4@CA started to release hydrogen at215℃, and reached its maximal desorption at36℃, much lower than those of the neat LiBH4. And a weight loss of8.86wt%was occurred at350℃in half an hour.(2) The desorption behavour of LiBH4confined in porous CA@CoNiB by a chemical impregnation technique was systematically investigated. The onset dehydrogenation temperature of the obtained sample LiBH4@CA@CoNiB was192 ℃, with the major hydrogen liberating at320℃. Furthermore, there was about15.9wt%hydrogen emitted when the temperature was up to600℃. In addition, the above sample had a superior desorption kinetic.9.33wt%H2was desorbed in30min at350℃, while bulk LiBH4released only2.13wt%H2. Further kinetic analysis based on JMA model demonstrated that the apparent activation energy of LiBH4@CA@CoNiB was reduced sharply compared to that of pure LiBH4. The significantly enhanced hydrogen storage properties of LiBH4@CA@CoNiB were attributed to the synergetic effect of nanoconfinement of CA and catalysis of CoNiB.(3) The catalytic effects of CoNiB on the decomposition of2LiBH4/MgH2system were investigated. It was found that after adding10wt%CoNiB nanoparticles, the2LiBH4/MgH2showed an excellent dehydrogenation performance. The first and second peak desorption temperature of the sample2LiBH4/MgH2-10wt%CoNiB were315℃and417℃. Meanwhile, a hydrogen content of10.2wt%was occurred in6h at400℃. Meanwhile, the catalytic mechanism on dehydrogenation of2LiBH4/MgH2was put forward.