An amorphous nickel catalyst stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) was synthesized by reduction in an aqueous NaBH(4)/NH(3)BH(3) solution. Both the bare nickel catalyst and the PVP stabilized nickel catalyst contain grains with an amorphous structure after the reduction. The PVP stabilized nickel catalyst maintains high activity for hydrolysis of NH(3)BH(3) to generate a stoichiometric amount of hydrogen with the cycle number up to S, while the reaction rate in the presence of the bare nickel catalyst decreases with cycle number. After five cycles, the PVP stabilized nickel catalyst maintains the amorphous structure, while the agglomeration of nickel in the bare nickel catalyst is observed. The results indicate that PVP prevents agglomeration and crystallization of nickel nanoparticles, leading to higher durability than the bare nickel catalyst. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.