Hydrogen generation from sodium borohydride hydrolysis accelerated by zinc chloride without catalyst: A kinetic study

Sodium borohydride (NaBH4) hydrolysis offers significant advantages in hydrogen storage for fuel cells, but the hydrolysis requires the use of expensive catalysts, such as Ru and Pt alloys, or various supports. To explore low-cost and high activity catalysts, we use ZnCl2 to promote the hydrolysis rate of sodium borohydride. The mechanisms and apparent activation energy of these composites are discussed. Compared to the hydrolysis of pure NaBH4 (523 mL/g hydrogen in 2 h at 298 K), NaBH4 with 20 wt% ZnCl2 has the best hydrolysis performance with the hydrogen generation rates of 844 mL/g in 5 min, 1039 mL/g in 10 min and 1933 mL/g in 2 h at 298 K. The apparent activation energies of NaBH4 hydrolysis decreased from 79.5 kJ/mol in deionized water to 47.7 kJ/mol with the addition of 20 wt% ZnCl2. These results demonstrated that ZnCl2 could be a promising reagent to promote NaBH4 hydrolysis in a hydrogen generation system to replace noble metal catalysts.