Nickel ferrite platinum nanoparticles: Highly active catalyst in hydrolytic dehydrogenation of ammonia borane

Magnetically separable platinum(0) nanoparticles are obtained by depositing them on the surface of magnetic nickel ferrite powder. The reduction of H2PtCl6 with sodium borohydride on the surface of nickel ferrite powder results in the formation of Pt0/NiFe2O4 nanoparticles, which can be easily isolated from the reaction medium using an exterior magnet. Characterization reveals that platinum(0) nanoparticles are uniformly dispersed on the surface of NiFe2O4 support, with a particle size ranging from 2 to 4 nm. The Pt0/NiFe2O4 nanoparticles with a 0.25 % wt. Pt loading are found to be very active catalyst providing a turnover frequency of 2200 min−1 in releasing H2 from the hydrolysis of ammonia borane at 25.0 °C. Remarkably, the Pt0/NiFe2O4 (0.25 % wt. Pt) nanocatalyst retains 55 % of its initial activity in the fifth run of hydrolysis in the reusability test, still releasing 3 equivalents H2 per mole of ammonia borane. X-ray photoelectron spectroscopy analysis shows the presence of a strong interaction between platinum(0) nanoparticles and nickel ferrite support, which enhances the stability and catalytic activity of the Pt0/NiFe2O4 nanocatalyst. Such a strong platinum-support interaction is responsible for holding the nanoparticles tightly on the oxide surface and leads to a charge transfer from platinum(0) nanoparticles to support surface which is favorable for the catalytic activity.