First row transition metal ion-assisted ammonia−borane hydrolysis for hydrogen generation

Abstract

Ammonia−borane (AB) hydrolysis for the generation of hydrogen has been studied using first row transition metal ions, such as Co²⁺, Ni²⁺, and Cu²⁺. In the cases of cobalt- and nickel-assisted AB hydrolysis, amorphous powders are formed that are highly catalytically active for hydrogen generation. Annealing of these amorphous powders followed by powder X-ray diffraction measurements revealed the presence of Co(0) and Co₂B and Ni(0) and Ni₃B, respectively. On the other hand, copper-assisted AB hydrolysis was catalyzed by in situ generated H⁺ and Cu(0) nanoparticles. The reduction ability of AB for the realization of coinage metal nanoparticles from the respective metal salts has also been studied. These reduction reactions were found to be facile, affording colloids of pure metal nanoparticles. Nanoparticles prepared in this manner were characterized by UV−visible spectroscopy and high-resolution electron microscopy.