Theoretical study on the possibility of using silicon carbide nanotubes as dehydrogenation catalysts for ammonia-borane

The adsorption and decomposition of ammonia-borane (AB) on the surface of silicon carbide nanotubes (SiCNTs) was investigated using density functional theory. Five adsorption types and four reaction channels were identified. The most favorable reaction channel that generates a H-2 molecule is slightly endothermic; furthermore, the energy barrier for the decomposition of the AB molecule is only 9.6 kcal mol(-1). The side reactions that generate NH3 or BH3 are highly endothermic; therefore, the generation of side products can be depressed by decreasing the temperature. However, desorption of hydrogen atoms from the surface appears to be a more difficult step. The energy-barrier height for generation of a H-2 molecule and its subsequent desorption from the surface is approximately 34.2 kcal mol(-1). The migration of hydrogen atoms on the surface of SiCNTs involves lower energy than the desorption process, indicating that the desorption of H-2 molecules from the surface may be more complicated.