Hydrogen evolution kinetics during transition metal oxide-catalyzed ammonia borane hydrolysis

Abstract

This paper examines the feasibility of using transition metal oxides (cobalt, iron, copper, molybdenum, and vanadium oxides) as catalysts for ammonia borane (AB) hydrolysis. In our experiments, we used an aqueous solution containing 0.24 wt % AB. The amount of oxide catalysts was 10–40 mg. The hydrolysis process was run in the temperature range from 35 to 80°C. The highest hydrogen evolution rate was observed at a temperature of 80°C in the presence of cobalt and iron oxides (Co3O4 and Fe2O3 · nH2O). The data obtained for the cobalt and iron oxides demonstrate that the reaction is first-order in ammonia borane. We determined the rate constants of the process and its apparent activation energy: 47.5 kJ/mol for Co3O4 and 60.2 kJ/mol for Fe2O3 · nH2O. The cobalt and iron oxides were shown to be efficient catalysts for hydrogen production from aqueous AB solutions.