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Hydroxyapatite-supported cobalt(0) nanoclusters as efficient and cost-effective catalyst for hydrogen generation from the hydrolysis of both sodium borohydride and ammonia-borane

2012-03-20
Rakap, Murat
Özkar, Saim
Herein, we report the preparation, characterization, and catalytic use of cobalt(0) nanoclusters supported on hydroxyapatite in the hydrolysis of both basic sodium borohydride and ammonia-borane solutions. They were prepared in situ from the reduction of cobalt(II) ions adsorbed on hydroxyapatite with sodium borohydride. Hydroxyapatite-supported cobalt(0) nanoclusters were stable enough to be isolated as solid material and characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), attenuated total reflectance infrared (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. They are isolable, redispersible, highly active, and cost-effective catalysts for hydrogen generation from the hydrolysis of both sodium borohydride and ammonia-borane even at low concentrations and temperature, providing 25,600 and 7400 turnovers and maximum hydrogen generation rates of 5.0 and 2.2 LH2 min(-1) (gCo)(-1) by the hydrolysis of NaBH4 and H3NBH3 at 25.0 +/- 0.1 degrees C, respectively. Hydroxyapatite-supported cobalt(0) nanoclusters provide activation energy of 53 +/- 2 kJ/mol for the hydrolysis of sodium borohydride and 50 +/- 2 kJ/mol for the hydrolysis of ammonia-borane. (C) 2011 Elsevier B. V. All rights reserved.