Nanoalumina-supported rhodium(0) nanoparticles as catalyst in hydrogen generation from the methanolysis of ammonia borane

Abstract

Rhodium(0) nanoparticles were in situ formed from the reduction of rhodium(II) octanoate and supported on the surface of nanoalumina yielding Rh(0)/nanoAl2O3 which is highly active catalyst in hydrogen generation from the methanolysis of ammonia borane at room temperature. The kinetics of nanoparticle formation can be followed just by monitoring the volume of hydrogen gas evolved from the methanolysis of ammonia borane. The evaluation of the kinetic data gives valuable insights to the slow, continuous nucleation and autocatalytic surface growth steps of the formation of rhodium(0) nanoparticles. Rh(0)/nanoAl2O3 could be isolated and characterized by a combination of advanced analytical techniques including ATR-IR, PXRD, TEM, XPS, SEM, SEM-EDX and ICP-OES. The results reveal that rhodium(0) nanoparticles are highly dispersed on the surface of nanoalumina. The particle size of Rh(0)/nanoAl2O3 increases with the initial rhodium loading of nanoalumina. Rh(0)/nanoAl2O3 is highly active catalyst in hydrogen generation from the methanolysis of AB providing an exceptional initial turnover frequency of TOF=218min−1 at 25.0±0.5°C, which is the highest value ever reported for rhodium catalysts in hydrogen generation from the methanolysis of ammonia borane.