Herein, we report the in situ generation, isolation and characterization of cobalt(0) nanoparticles, stabilized by poly(4-styrenesulfonic acid-co-maleic acid), PSSMA, and their catalytic activity in the hydrolysis of hydrazine borane (HB). Cobalt(0) nanoparticles having average particle size of 3.1 +/- 0.5 nm were prepared by in situ reduction of cobalt(II) chloride in aqueous solution of hydrazine borane in the presence of PSSMA, isolated magnetically from the catalytic reaction solution using a magnet, and characterized by UV-Vis, TEM, EDX, XPS and ATR-IR techniques. PSSMA-stabilized cobalt(0) nanoparticles were found to be highly active catalyst in the hydrolysis of HB releasing nearly 3.0 equivalents of H-2 gas. They provide an initial turnover frequency of TOF = 370 h(-1) (6.2 min(-1)) for the hydrolysis of HB at 25.0 +/- 0.5 degrees C. They are also long-lived catalyst providing 3070 turnovers in hydrogen generation from the hydrolysis of NB over 45 h at room temperature. Our report also includes (i) the collection of wealthy kinetic data to demonstrate the effect of hydrazine borane and catalyst concentrations on the hydrogen generation rate and to determine the rate law for the catalytic hydrolysis of HB, (ii) the investigation of the effect of temperature on the rate of hydrogen generation and determination of activation parameters (E-a, Delta H-#, and Delta S-#) for the catalytic hydrolysis of HB, (iii) the results of poisoning experiments and filtration tests showing that cobalt(0) nanoparticles are the kinetically competent heterogeneous catalyst. PSSMA-stabilized cobalt(0) nanoparticles are isolable, redispersible in water, reusable and long-lived catalyst in hydrogen generation from the hydrolysis of HB. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.