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Article Citation - WoS: 24Citation - Scopus: 28Palladium(0) Nanoparticles Supported on Hydroxyapatite Nanospheres: Active, Long-Lived, and Reusable Nanocatalyst for Hydrogen Generation From the Dehydrogenation of Aqueous Ammonia-Borane Solution(Springer, 2014) Karatas, Yasar; Yurderi, Mehmet; Gulcan, Mehmet; Zahmakiran, Mehmet; Kaya, MuratAmong the solidmaterials considered in the chemical hydrogen storage, ammonia-borane (NH3-BH3) appears to be one of the promising candidates as it can release hydrogen throughout hydrolysis in the presence of suitable catalyst under mild conditions. Herein we report, for the first time, the preparation and characterization of palladium(0) nanoparticles supported on nanohydroxyapatite and their catalytic use in the hydrolysis of ammonia-borane under air at room temperature. These new palladium(0) nanoparticles were generated in situ during the catalytic hydrolysis of ammonia-borane starting with palladium(II) immobilized nanohydroxyapatite. The preliminary characterization of the palladium(0) nanoparticles supported on nanohydroxyapatite was done by the combination of complimentary techniques, which reveals that the formation of well-dispersed Pd(0)NPs nanoparticles (1.41 +/- 0.52 nm) on the surface of hydroxyapatite nanospheres (60-150 nm). The resulting palladium nanocatalyst achieves hydrogen generation from the hydrolysis of ammonia-borane with an initial turnover frequency value (TOF) of 11 mol H-2 mol(-1) Pd x min at room temperature under air. In addition to their high activity, the catalytic lifetime experiment showed that they can also act as a long-lived heterogeneous catalyst for this reaction (TTON = 14,200 mol H-2 mol(-1) Pd) at room temperature under air. More importantly, nanohydroxyapatite- supported palladium(0) nanoparticles were found to be highly stable against to leaching and sintering throughout the catalytic runs that make them isolable, bottleable, and reusable heterogeneous catalyst for the hydrolysis of ammonia-borane.Article Citation - WoS: 125Citation - Scopus: 133Supported Copper-Copper Oxide Nanoparticles as Active, Stable and Low-Cost Catalyst in the Methanolysis of Ammonia-Borane for Chemical Hydrogen Storage(Elsevier Science Bv, 2015) Yurderi, Mehmet; Bulut, Ahmet; Ertas, Ilknur Efecan; Zahmakiran, Mehmet; Kaya, MuratThe physical mixture of copper (Cu) copper(I) oxide (Cu2O) and copper(II) oxide (CuO) nanoparticles supported on activated carbon (Cu-Cu2O-CuO/C) were reproducibly prepared by a simple deposition-reduction technique without using any stabilizer in water at room temperature. The characterization of the resulting material by ICP-OES, P-XRD, XPS, DR-UV/vis, BFTEM and HRTEM techniques reveals that the formation of well-dispersed highly crystalline 3.8 +/- 1.7 nm nanoparticles on the surface of activated carbon. These carbon supported Cu-Cu2O-CuO nanoparticles were employed as heterogeneous catalyst in the methanolysis of ammonia-borane (NH3BH3), which has been considered as one of the attractive materials for the efficient storage of hydrogen, under mild conditions. We found that only 3.0 mol % Cu-Cu2O-CuO/C catalyst is enough to catalyze the methanolysis of ammonia-borane with high activity (TOF = 24 min(-1)) and conversion (>99%) at room temperature. More importantly, the exceptional stability of supported Cu-Cu2O-CuO nanoparticles against to sintering and leaching make Cu-Cu2O-CuO/C recyclable catalyst for the methanolysis of ammonia-borane. Cu-Cu2O-CuO/C catalyst retains >76% of its initial activity with 94% of conversion even at 8th recycle in the methanolysis of ammonia-borane at complete conversion. The study reported here also includes the collection of kinetic data for Cu-Cu2O-CuO/C catalyzed methanolysis of ammonia-borane depending on catalyst [Cu], substrate [NH3BH3] concentrations and temperature to determine the rate expression and the activation parameters (E-a, Delta H-#, and Delta S-#) of the catalytic reaction. (C) 2014 Published by Elsevier B.V.
