In our previous report, about 1 equiv.H(2) can be evolved from a Fe-modified ammonia borane (AB) sample at a temperature as low as 60 degrees C with significant depression of induction period, sample foaming and toxic byproducts [1]. In this study, the effects of catalyst precursors and catalyst loading were investigated on the hydrogen desorption profile and the formation of crystalline polyaminoborane (PAB). The experimental results show that loading 2.0 mol.% FeCl(3) to solid-state AB gives the best performance of formation of crystalline PAB. The rate of hydrogen evolution from the Fe-modified AB is 5.8 times as that of neat AB at 60 degrees C. X-ray absorption spectroscopy (XAS) and quasi in situ (57)Fe Mossbauer characterizations show that Fe-B nanoalloy, which functions as catalytic species in the dehydrogenation, is formed upon mixing AB with FeCl(3). Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.