An Investigation On The Hydrogen Storage Properties Of LiBH₄ Catalyzed And Confined By The Porous Mixed Metal Oxide Materials

With the development of the world,the demands of energy are rapidly increased.While,the scarce of traditional energy including coal,petroleum,natural gas makes people center their attention on the efficient,sustainable and pollution-free new energy.Hydrogen,due to its abundance,high combustion efficiency and no pollution,is known as a promising energy-storage medium.Hydrogen is playing an important role in the fields of fuel cell and onboard hydrogen storage and many countries have made it as key research projects.The obstacle that restricts the hydrogen application is the hydrogen storage system.Recently,tremendous efforts have been devoted to high-weight metal hydrides and complex hydrides.Among them,Li BH₄ has drawn extensively attention for its high hydrogen storage capacities(18.5 wt%,121 kg m^-3).Unfortunately,it has been limited in applications because of the thermodynamic stability,low kinetics of their reversible hydrogen release.Thus,novel strategies have been found to enhance the hydrogen storage performance of LiBH₄,such as doping the effective catalysts and nanoconfinement in the nanoporous materials.Porous metal oxide ZnCo₂O₄/ZnO nanosheets and microsphere NiMnO₃nanoparticles were fabricated in this work,which were used as catalysts and the carrier to confine LiBH₄.X-ray diffraction is used to characterize the structure of Li BH₄ in the scaffolds,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）are used to measure the morphology of thematerials;TPD（Temperature-programmed-desorption）measurements,Sievert-type apparatus（advanced materials Corporation）at various temperatures（PCT）,Differential Scanning Calorimetry（DSC）are carried out to detect the hydrogen desorption performance.（1）3D hierarchical porous ZZCO nanosheets are successfully synthesized by the reflux method and followed by thermal decomposition at 500°C in the air atmosphere.Then Li BH₄ nanoparticles are confined into porous ZZCO nanosheets via the chemical impreganation means.And we systematically investigated the desorption properties of LiBH₄@xZZCO.The results show that the dehydrogenation temperature of composites decreased compared to pure Li BH₄,especially for the Li BH₄@2ZZCO sample.The onset desorption temperature is 169°C and the maximal dehydrogenation peak occurs at around 275°C,150°C,170°C lower than the neat LiBH₄,respectively.Meantime,the composite demonstrates excellent dehydrogenation kinetics,with 3.1 wt%hydrogen released from Li BH₄ at 300°C within 30 min.These results reveal that ZZCO as confining agent and catalyst plays a significant role on lowing desorption temperature and enhancing hydrogen released kinetics.（2）Microsphere Ni MnO₃ particles are successfully prepared by simple stirring at proper temperature and then followed by the thermal treatment at 500°C in air for2 h.LiBH₄ is incorporated into porous NiMnO₃ particles and the dehydrogenation behavior of composites is researched.The composite starts liberate hydrogen at130°C and the major hydrogen liberation takes place at 300°C.Simultaneously,the mixture also shows the outstanding desorption dynamics,releasing total about 2.15wt%hydrogen at 300°C within 30 min.DSC measurements give evidence that the activation energy of LiBH₄@NiMnO₃ is reduced to 129.8 kJ/mol,which further confirms the superior dehydrogenation performance of the composite.