Nanozirconia supported ruthenium(0) nanoparticles: Highly active and reusable catalyst in hydrolytic dehydrogenation of ammonia borane

Abstract

Nanozirconia supported ruthenium(0) nanoparticles (Ru⁰/ZrO₂) were prepared by impregnation of ruthenium(III) cations on the surface of zirconia followed by their reduction with sodium borohydride at room temperature. Ru⁰/ZrO₂ was isolated from the reaction solution by centrifugation and characterized by ICP-OES, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on zirconia and the resulting Ru⁰/ZrO₂ is a highly active and reusable catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 173 min^-1 at 25 °C. The reusability and catalytic lifetime tests reveal that Ru⁰/ZrO₂ is still active in the subsequent runs of hydrolysis of ammonia borane preserving 67% of the initial catalytic activity even after the fifth run and Ru⁰/ZrO₂ provides 72,500 turnovers (mol H₂/mol Ru) before deactivation at 25 °C. Our report also includes the results of kinetic studies depending on the catalyst concentration and temperature to determine the activation energy (E_a = 58 ± 2 kJ/mol) for hydrolytic dehydrogenation of AB.

Keywords: Ammonia borane; Hydrogen generation; Ruthenium nanoparticles; Zirconia.