Controllable hydrogen generation performance from Al/NaBH4 composite activated by La metal and CoCl2 salt in pure water

Abstract

A novel composition of Al/NaBH4 mixture activated by La and CoCl2 in water for hydrogen generation was investigated. The composition had good stability at 298 K with high La content and low CoCl2 content, but presented good hydrogen generation performance with increasing global temperature. For example, The Al-15 wt.%La-5 wt.%CoCl2/NaBH4 mixture (mass ratio of 1:1) yielded 1664 ml hydrogen/1 g mixture with 100% efficiency within 60 min at 333 K. The hydrogen generation rate and amount could be regulated by changing composition design, hydrolytic conditions, etc. There existed a synergistic effect of La and CoCl2. Increasing La content was helpful to decrease crystal size of the mixture, but its hydrolysis byproduct La(OH)3 deposited on Al surface and had side effect on Al hydrolysis. Increased CoCl2 content was attributed to the producing of more actively catalytic sites Co2B/Al(OH)3 formed in the hydrolytic process. Co2B had dual catalytic effect on Al/NaBH4 hydrolysis. It deposited on Al surface and acted as a cathode of a micro galvanic cell. Co2B/Al(OH)3 was also a good promoter to NaBH4 hydrolysis. Therefore, the Al/NaBH4 mixture activated by La and CoCl2 may be applied as hydrogen generation material and the experimental data lays a foundation for designing practical hydrogen generators.