Palladium(0) Nanoparticles Supported on Silica-Coated Cobalt Ferrite: a Highly Active, Magnetically Isolable and Reusable Catalyst for Hydrolytic Dehydrogenation of Ammonia Borane

Abstract

Palladium(0) nanoparticles supported on silica-coated cobalt ferrite (Pd(0)/SiO2-CoFe2O4) were in situ generated during the hydrolysis of ammonia borane, isolated from the reaction solution by using a permanent magnet and characterized by ICP-OES, XRD, TEM, TEM-EDX, XPS and the N-2 adsorption-desorption techniques. All the results reveal that well dispersed palladium(0) nanoparticles were successfully supported on silica coated cobalt ferrite and the resulting Pd(0)/SiO2-CoFe2O4 are highly active, magnetically isolable, and recyclable catalysts in hydrogen generation from the hydrolysis of ammonia borane with an unprecedented turnover frequency (TOF, calculated on the basis of the total amount of Pd) of 254 mol H-2 (mol Pd min)(-1) at 25 +/- 0.1 degrees C. The reusability tests reveal that Pd(0)/SiO2-CoFe2O4 are still active in the subsequent runs of hydrolysis of ammonia borane providing 100% conversion. Pd(0)/SiO2-CoFe2O4 provide the highest catalytic activity with a TOF value of 198 mol H-2 (mol Pd min)(-1) in the 10th use in hydrogen generation from the hydrolysis of ammonia borane as compared to the other palladium catalysts. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy of the reaction (E-a = 52 +/- 2 kJ/mol) and the effect of catalyst concentration on the rate of hydrolytic dehydrogenation of ammonia borane, respectively. (C) 2013 Elsevier B.V. All rights reserved.