Kinetic Assessment of Catalysts for the Methanolysis of Sodium Borohydride for Hydrogen Generation

The efficacy of metal chlorides and platinum-coated lithium cobalt oxide as catalysts for the methanolysis of sodium borohydride over 45 to −20 °C was investigated. Among the metal chlorides tested, cobalt chloride exhibited maximum activity. In the presence of metal chlorides, the methanolysis reaction exhibited first-order kinetics with respect to the borohydride concentration. The rate constant for methanolysis reaction at −20 °C for 10 wt% cobalt chloride was determined to be 0.00136 s−1, which represents an over 100 times increase compared to the kinetics of the noncatalyzed methanolysis reaction. Platinum-coated lithium cobalt oxide also exhibits a significant rate increase compared to uncatalyzed methanolysis reaction at at 20 °C; however, no measurable activity was noticed at −20 °C. Further, the reaction kinetics appear to be zeroth-order with respect to borohydride concentration. In addition to the rate enhancement, all potential catalysts tested in this study showed a significant reduction in the lag time to less than 5 min at all temperatures. The activity of both cobalt chloride and platinum-coated lithium cobalt oxide were examined over several cycles and both catalysts had a reduced activity after the first cycle; however, the rate of hydrogen generation remained stable for the subsequent cycles.