▎ 摘　　要

Well-dispersed Ag@Co core-shell nanoparticles (NPs) supported on graphene with controlled compositions were synthesized by the reduction of silver nitrate, cobalt(II) acetate, and graphene oxide (GO) in the presence of hydrazine and ethylene glycol. These NPs were composition dependent catalysts for hydrogen generation from the hydrolysis of ammonia borane. Among all Ag@Co catalysts tested, the Ag-0.5@Co-0.5/graphene NPs exhibited the highest catalytic activity, with the turnover frequency (TOF) value of 10.5 mol H-2 min(-1) (mol catalyst)(-1), and activation energy value of 39.33 kJ/mol. Kinetic studies reveal that the catalytic hydrolysis of AB and MeAB are both first order with respect to the catalyst concentrations. Furthermore, the Ag-0.5@Co-0.5/graphene NPs show good durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB and MeAB, which makes the practical recycling application of the catalyst more convenient. (C) 2013 Elsevier B.V. All rights reserved.