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Water dispersible acetate stabilized ruthenium(0) nanoclusters as catalyst for hydrogen generation from the hydrolysis of sodium borohyride

Zahmakiran, Mehmet
Özkar, Saim
The development of new storage materials will facilitate the use of hydrogen as a major energy vector in near future. In the hydrogen economy, chemical hydrides such as NaBH4, KBH4, LiH, NaH have been tested as precursor materials for supplying hydrogen at ambient temperature. Among these chemical hydrides, sodium borohydride (NaBH4) provides a safe and practical mean of producing hydrogen. Sodium borohydride is stable in basic solution; however, hydrolysis generates hydrogen gas in the presence of a suitable catalyst. All of the prior catalysts having been used for this hydrolysis reaction are heterogeneous and, therefore, have limited activity because of the surface area. Here, we report the employment of water dispersible metal(0) nanoclusters as catalyst for the hydrolysis of sodium borohydride. The water dispersible ruthenium(0) nanoclusters were prepared from the reduction of RuCl3 center dot 3H(2)O and stabilized by using acetate ion. They provide 5170 turnovers in the hydrolysis of sodium borohydride at 25.0 +/- 0.1 degrees C before deactivation. The acetate stabilized ruthenium(0) nanoclusters of 2.8 +/- 1.4 nm particle size were characterized by TEM, XPS, and FTIR spectroscopy. Kinetic study shows that the ruthenium(0) nanocluster-catalyzed hydrolysis of sodium borohydride is first order in catalyst concentration and zero order in substrate concentration. The acetate stabilized ruthenium(0) nanoclusters provide a low activation energy for the hydrolysis of sodium borohydride. Even in basic solution, the activation energy was found to be smaller than that obtained by using the carbon-supported ruthenium as catalyst. (c) 2006 Elsevier B.V. All rights reserved.