Synthesis of solid-state NaBH_4/Co-based catalyst composite for hydrogen storage through a high-energy ball-milling process

摘要

Solid-state composites of NaBH_4 and Co-based catalyst have been fabricated for hydrogen generation via a novel mechanochemical technique, i.e. the high-energy ball milling, in which the gravimetric storage capacity of hydrogen has reached 6.7 wt%, meeting the 2010 target of at least 0.06 kg H_2/kg set by the U.S. Department of Energy (DOE). The active catalysts used in the hydrolysis reaction of sodium borohydride for hydrogen generation are mainly cobalt oxides. Controlled addition of water, namely water used as a limiting agent, to the solid composites of NaBH_4 and Co-based catalyst greatly improves the H_2 storage capacity and resolved the issues of low gravimetric H_2 storage in conventional aqueous system of sodium borohydride. Factors influencing the performance of hydrogen production such as amounts of H_2O added, catalyst loadings and durations of ball-milling processes are investigated. Moreover the hydrolyzed products of NaBH_4 and spent catalysts are analyzed as well.