Ceria supported ruthenium nanoparticles: Remarkable catalyst for H2 evolution from dimethylamine borane

Abstract

Ceria supported ruthenium nanoparticles (Ru0/CeO2) are synthesized by impregnation of Ru3+ ions on CeO2 powders followed by sodium borohydride reduction of Ru3+/CeO2. Their characterization was achieved using analytical methods including TEM, XRD, BET, SEM, and XPS. All the results reveal the formation of ruthenium(0) nanoparticles in 1.8 ± 0.3 nm size on CeO2 support. Ru0/CeO2 nanoparticles show high activity in catalyzing the H2 evolution from dimethylamine borane (DMAB). Ru0/CeO2 nanoparticles with 0.55% wt Ru provide the highest turnover frequency (812 h−1) for releasing H2 from DMAB at 60 °C and a total of 2500 turnovers before deactivation. High activity of Ru0/CeO2 nanoparticles for catalytic dehydrogenation of DMAB is attributable to the reducible nature of CeO2 support. Ce3+ defects formation in ceria under reducing conditions of dehydrogenation causes accumulation of negative charge on the oxide support, which makes oxide surface attractive for the ruthenium(0) nanoparticles. This, in turn, causes an enhancement in the metal-support interaction and thus in catalytic activity. The XPS analysis of bare ceria and Ru0/CeO2 demonstrates the increase in the concentration of Ce3+ defects after catalysis. Ru0/CeO2 nanoparticles are also reusable catalyst for H2 evolution from DMAB retaining 40% of initial activity after 4th run of reaction. The catalytic activity of Ru0/CeO2 nanoparticles and activation energy of catalytic dehydrogenation are compared with those of the other ruthenium based catalysts known in literature.