Quasi in situ Mössbauer and XAS studies on FeB nanoalloy for heterogeneous catalytic dehydrogenation of ammonia borane

In our previous report, about 1 equiv. H2 can be evolved from a Fe-modified ammonia borane (AB) sample at a temperature as low as 60 °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.% FeCl3 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 °C. X-ray absorption spectroscopy (XAS) and quasi in situ 57Fe Mössbauer characterizations show that Fe–B nanoalloy, which functions as catalytic species in the dehydrogenation, is formed upon mixing AB with FeCl3.