Quasi In Situ Mössbauer Spectroscopic Studies on Novel Hydrogen Storage Material of Fe-Modified Ammonia Borane

Ammonia borane (AB in short, NH3BH3) with a hydrogen content of 19.6 wt % has attracted increasing attention as a promising hydrogen storage material. One of the challenges in its practical usage is how to improve its dehydrogenation ability. Among various approaches, the direct transition metal (Co, Ni and Fe) modification of solid phase AB reported by Chen’s group very recently has been proved to be a very exciting method. In case of Fe-modified AB, the rate of hydrogen evolution from the Fe-modified AB is 5.8 times as that of pristine AB at a temperature as low as 60 °C with significant depression of induction period, sample foaming and toxic byproducts. In this presentation, quasi in situ 57Fe Mössbauer and X-ray adsorption fine structure (XAFS) techniques are employed to identify the changes of Fe chemical environment during dehydrogenation process. The experimental results show that FeB nanoalloy is formed upon mixing AB with FeCl3 which probably functions as catalytic species in the dehydrogenation process