Calcination treatment is an important step in preparation of supported transition metal catalysts that are effective for promoting the hydrolysis reaction of sodium borohydride. We found that calcination treatment of cobalt-tungsten-boron/nickel foam catalysts results in the appearance of an induction period in their first time use, and the duration of which depends on the calcination temperature and atmosphere. Upon reusing the catalysts, the induction period completely disappeared. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and synchronous thermal analyses techniques were employed to study the mechanism underlying the induction period phenomenon. Our study results showed that the appearance/disappearance of the induction period should be correlated with the desorption/reabsorption of hydrogen in the catalysts. (C) 2010 Elsevier B.V. All rights reserved.