Palladium(0) nanoparticles supported on polydopamine coated CoFe2O4 as highly active, magnetically isolable and reusable catalyst for hydrogen generation from the hydrolysis of ammonia borane

Abstract

Palladium(0) nanoparticles supported on cobalt ferrite (Pd0/CoFe2O4) are found to be highly active catalyst, providing an unprecedented catalytic activity with a turnover frequency of 290min−1 in hydrogen generation from the hydrolysis of ammonia borane at room temperature. However, the initial catalytic activity of Pd0/CoFe2O4 catalyst is not preserved after the reuse of the catalyst in hydrolytic dehydrogenation of ammonia borane. The stability of the catalyst is improved by using the polydopamine (PDA) coated cobalt ferrite as support instead of bare cobalt ferrite. PDA coating of CoFe2O4 nanopowders was achieved by pH-induced self-polymerization of dopamine hydrochloride at room temperature and the thickness of PDA was optimized by changing the amount of dopamine hydrochloride. Palladium(0) nanoparticles supported on PDA coated cobalt ferrite (Pd0/PDA–CoFe2O4) were prepared by two step impregnation-reduction process and characterized by a combination of advanced analytical techniques. The results reveal that palladium nanoparticles with an average size of 1.4±0.3nm are well dispersed on polydopamine layer with a thickness of 8.6±1.0nm on the surface of cobalt ferrite nanopowders. Pd0/PDA–CoFe2O4 with a palladium loading of 1.08wt% was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency of 175min−1 at 25.0±0.1°C. Magnetically isolable Pd0/PDA–CoFe2O4 catalyst preserves its initial catalytic activity even after the tenth use providing the release of 3 equivalent H2 per mole of ammonia borane.