Abstract Solid-state hydrogen storage is of considerable concern as a potential hydrogen source for portable fuel cell applications. This study mainly focuses on kinetics of NaBH4/Al2O3 nanoparticles (20 nm)/H2O system with CoCl2 as catalyst and the factors that affect the hydrogen generation rate (HGR). It is observed that the reaction rate increases considerably with increase in NaBH4, Al2O3 nanoparticle (20 nm), CoCl2 and NaOH concentrations and the respective reaction orders are calculated. Hydrogen generation rate is also investigated at different temperatures (303, 313, 323 and 333 K) for constant NaBH4 (1.25 moles/L), NaOH (1.4 moles/L), CoCl2 (0.02 moles/L) and Al2O3 (0.09 moles/L) concentrations. Kinetics of the NaBH4 hydrolysis reaction increases with γ-Al2O3 nanoparticles and the calculated activation energy is 29 kJ/moles. This study also reports that a combined dual-solid-fuel system is highly efficient in terms of hydrogen storage capacities compared with a single hydride based system. Maximum hydrogen generation efficiency, observed at a mass ratio of 0.09: 0.7 (Al2O3/NaBH4), is 99.34%.

Abstract A hydrogen generation system based on NaBH4 hydrolysis is affected by the nature of the catalyst and catalyst promoter. Various catalyst promoters such as Al2O3 nanoparticles, Al2O3 particles, ZrO2 sand, SiO2, MMT clay, CNT and zeolite are compared with respect to hydrogen generation (HG) and hydrogen generation rate (HGR). The highest HG and HGR are observed with alumina nanoparticles as compared to other promoters. Cobalt chloride is found to be most efficient catalyst among the other cobalt based salts (CoCl2.6H2O, CoSO4.7H2O, (CH3COO)2Co.4H2O, Co(NO3)2.H2O), cadmium based salt (CdSO4) and copper based salt (CuSO4.5H2O). Maximum HGR obtained is 19.47 moles/L.sec for NaBH4 (1.26 moles/L)/Al2O3 nanoparticles (0.12 moles/L)/H2O and CoCl2.6H2O (0.02 moles/L) as catalyst at room temperature and atmospheric pressure. NaBH4 and alumina hydrolysis reactions, hydrophilic and amphoteric nature of alumina, affinity of Co+2 towards BH4 - ions and formation of aluminates are the factors that promote HGR, as illustrated in this work. Residue obtained from hydrolysis reaction is characterized for its elemental composition by the EDS technique, which confirmed a maximum percentage of boron in the residue. XRD and FTIR results concluded that adsorption of Na+ and Co+ ions occurred on the alumina surface and resulted in the formation of sodium aluminates and cobalt aluminates in the solution.