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    Öğe
    Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature
    (Mdpi Ag, 2015) Durap, Feyyaz; Caliskan, Salim; Ozkar, Saim; Karakas, Kadir; Zahmakiran, Mehmet
    Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 +/- 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min(-1) in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain similar to 80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.
  • [ X ]
    Öğe
    Hydrogen liberation from the hydrolytic dehydrogenation of dimethylamine-borane at room temperature by using a novel ruthenium nanocatalyst
    (Royal Soc Chemistry, 2012) Caliskan, Salim; Zahmakiran, Mehmet; Durap, Feyyaz; Ozkar, Saim
    Herein we report the discovery of an in situ generated, highly active nanocatalyst for the room temperature dehydrogenation of dimethylamine-borane in water. The new catalyst system consisting of ruthenium(0) nanoparticles stabilized by the hydrogenphosphate anion can readily and reproducibly be formed under in situ conditions from the dimethylamine-borane reduction of a ruthenium(III) precatalyst in tetrabutylammonium dihydrogenphosphate solution at 25 +/- 0.1 degrees C. These new water dispersible ruthenium nanoparticles were characterized by using a combination of advanced analytical techniques. The results show the formation of well-dispersed ruthenium(0) nanoparticles of 2.9 +/- 0.9 nm size stabilized by the hydrogenphosphate anion in aqueous solution. The resulting ruthenium(0) nanoparticles act as a highly active catalyst in the generation of 3.0 equiv. of H-2 from the hydrolytic dehydrogenation of dimethylamine-borane with an initial TOF value of 500 h(-1) at 25 +/- 0.1 degrees C. Moreover, they provide exceptional catalytic lifetime (TTO = 11 600) in the same reaction at room temperature. The work reported here also includes the following results; (i) monitoring the formation kinetics of the in situ generated ruthenium nanoparticles, by using the hydrogen generation from the hydrolytic dehydrogenation of dimethylamine-borane as a catalytic reporter reaction, shows that sigmoidal kinetics of catalyst formation and concomitant dehydrogenation fits well to the two-step, slow nucleation and then autocatalytic surface growth mechanism, A -> B (rate constant k(1)) and A + B -> 2B (rate constant k(2)), in which A is RuCl3 center dot 3H(2)O and B is the growing, catalytically active Ru(0)(n) nanoclusters. (ii) Hg(0) poisoning coupled with activity measurements after solution infiltration demonstrates that the in situ generated ruthenium(0) nanoparticles act as a kinetically competent heterogeneous catalyst in hydrogen generation from the hydrolytic dehydrogenation of dimethylamine-borane. (iii) A compilation of kinetic data depending on the temperature and catalyst concentration is used to determine the dependency of reaction rate on catalyst concentration and the activation energy of the reaction, respectively.