Zeolite-Confined Ruthenium(0) Nanoclusters Catalyst: Record Catalytic Activity, Reusability, and Lifetime in Hydrogen Generation from the Hydrolysis of Sodium Borohydride

Sodium borohydride, NaBH4, has been considered the most attractive hydrogen-storage material for portable fuel cell applications,,is it provides a safe and practical means of producing hydrogen. In a recent communication (Zahmakiran, M.; Ozkar, S. Langmuir 2008, 24, 7065), we have reported a record total turnover number (TTON) of 103 200 mol H-2/mol Ru and turnover frequency (TOF) up to 33 000 mol H-2/mol Ru center dot h obtained by using intrazeolite ruthenium(0) nanoclusters in the hydrolysis of sodium borohydride. Here we report full details of die kinetic studies on the intrazeolite ruthenium(0) nanoclusters catalyzed hydrolysis of sodium borohydride in both aqueous and basic solutions. Expectedly, the intrazeolite ruthenium(0) nanoclusters show unprecedented catalytic lifetime, TTON = 27 200 mol H-2/mol Ru, and TOF up to 4000 mot H-2/mol Ru center dot h in the hydrolysis of sodium borohydride in basic solution (5% wt NaOH) as well. More importantly, the intrazeolite ruthenium(0) nanoclusters are isolable, bottleable, redispersible, and yet catalytically active. They retain 76% or 61% of their initial catalytic activity at the fifth run with a complete release of hydrogen in aqueous and basic medium, respectively. The intrazeolite ruthenium(0) nanoclusters were isolated is black powder and characterized by using a combination of advanced analytical techniques including XRD, HRTEM, TEM-EDX, SFM, XPS, ICP-OES, and N-2 adsorption.