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Ceria supported manganese(0) nanoparticle catalysts for hydrogen generation from the hydrolysis of sodium borohydride

Özkar, Saim
Herein we report for the first time the preparation and catalytic use of the ceria supported manganese(0) nanoparticles in hydrogen generation from the hydrolysis of sodium borohydride. They are in situ formed from the reduction of manganese(II) ions on the surface of ceria nanopowders during the catalytic hydrolysis of sodium borohydride in aqueous solution at room temperature. Manganese(0) nanoparticles are isolated from the reaction solution by centrifugation and characterized by a combination of analytical techniques. Nanoceria supported manganese(0) nanoparticles are highly active and long-lived catalysts providing a turnover frequency of 417 h(-1) and 45,000 turnovers in hydrogen generation from the hydrolysis of sodium borohydride at 25.0 +/- 0.1 degrees C. They also have high durability as they retain 55% of their initial catalytic activity after the fifth cycle of hydrolysis providing a release of 4 equivalent H-2 gas per mol of sodium borohydride. The noticeable activity loss in successive runs of hydrolysis is attributed to the deactivation due to agglomeration. High activity and stability of ceria supported manganese(0) nanoparticles are ascribed to the unique nature of reducible cerium oxide. The formation of cerium(III) defects under catalytic conditions provides strong binding for the manganese(0) nano particles to oxide surface which makes the catalytic activity and stability favorable. Our report also includes the results of kinetic study of catalytic hydrolysis of sodium borohydride depending on the temperature, catalyst and substrate concentration. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.