Ultrahigh Catalytic Activity of l-Proline-Functionalized Rh Nanoparticles for Methanolysis of Ammonia Borane.

The synthesis of ultrafine and well-distributed rhodium nanoparticles (NPs) with high efficiency toward methanolysis of ammonia borane (AB) is crucially important but challenging. A facile approach has been developed for synthesizing ultrafine and uniform Rh NPs deposited on carbon by using the small soluble organic molecule (SOM) of l-proline (PRO) as capping agent (Rh-PRO/C). The enrichment of N,O-coordination sites for the metal precursor by using PRO was found to be the key to the synthesis Rh-PRO/C. The as-prepared Rh-PRO/C showed high catalytic activity for ammonia borane methanolysis with the highest total turnover frequency (TOF) of 1035 mol H 2  (molRh  min)-1 under basic conditions, which was three times higher than that of the state-of-the-art Rh-based catalysts. The excellent catalytic performance of Rh-PRO/C was ascribed to the well-dispersed Rh NPs and the PRO-functionalized metal surface, which can provide more active sites for the reaction. The merit of size-controlled synthesis combined with metal NP surface modification by SOMs is likely to be beneficial in various catalytic fields.