In situ facile synthesis of Rh nanoparticles supported on carbon nanotubes as highly active catalysts for H2 generation from NH3BH3 hydrolysis

Abstract

In this work, carbon nanotubes (CNTs) supported rhodium nanoparticles (Rh NPs) (Rh(0)/CNTs) have been successfully prepared via a very simple in situ method and used as the catalysts for hydrogen generation from the hydrolysis of ammonia borane (AB, NH3BH3) under ambient atmosphere at room temperature. The as-synthesized nanocatalysts were characterized by XRD, SEM, TEM, EDX, ICP, and XPS measurements. The characterized results revealed that ultrafine Rh NPs of about 1.1–3.4 nm were well-dispersed on CNTs. Compared with free Rh(0) NPs and Rh(0)/activated charcoal, the Rh(0)/CNTs showed higher catalytic activity for the hydrolysis of NH3BH3 with a total turnover frequency (TOF) value up to 706 mol H2 (mol Rh min)−1, which was among the highest of all the heterogeneous catalysts ever reported for the same reaction. The recyclability tests revealed that the Rh(0)/CNTs are still active after five runs of hydrolysis of NH3BH3 providing 100% conversion and retaining 61% of their initial catalytic activity (TOF = 431 mol H2 (mol Rh min)−1). In addition, the activation energy for the hydrolysis of NH3BH3 catalyzed by Rh(0)/CNTs was measured to be 32 ± 1 kJ/mol, which was lower than most of the values reported for other catalysts.