Abstract
Ammonia borane (NH 3BH 3) with its high hydrogen content (19.6 % per mass) and mild desorption conditions has the potential to meet the onboard hydrogen storage requirements for vehicular applications. Ammonia borane decomposes in three steps at the temperatures of about 100 °C, 140 °C and 1000 °C respectively, releasing one mole equivalent of hydrogen in each step. The major obstacle towards the use of AB as a hydrogen store is the poor kinetics and irreversibility of the reaction products. With the use of catalyst, the decomposition temperature could be reduced and the kinetics can be improved. In the current work, misch metal (Mm) nanoparticles are used as catalyst. These nanoparticles were synthesized using ball milling and characterized. Homogeneous mixture of AB and catalyst was prepared in the ratio 10:1 using ball milling. Isothermal as well as non-isothermal studies were performed on neat AB and AB with Mm nanoparticles. Samples as well as solid residues of the decomposition reaction were characterized using XRD and FTIR. It was observed that with catalyst, AB starts releasing hydrogen even at room temperature and the induction period was found to be practically absent. Misch metal is found to be a good catalyst for ammonia borane decomposition.
Highlights
Hydrogen storage is one of the biggest issues associated with the transformation of fossils fuel scenario to hydrogen economy (Schlapbach & Züttel, 2001)
X-ray diffraction pattern of Ammonia Borane (AB) and ABMm, before and after decomposition is compared in the Fig. 1
As the decomposition temperature increases, NH and B-H bands are broadened and disappear. Disappearance of these two bonds is the prime evidence of hydrogen formation from AB molecules. It can be seen from the figure that B-N band near 500 cm-1 is not disrupted even after decomposition at 150 °C which rules out the breaking of ammonia borane molecule (H3N-BH3) at the middle and there is no possibility of ammonia or diborane gas formation
Summary
Hydrogen storage is one of the biggest issues associated with the transformation of fossils fuel scenario to hydrogen economy (Schlapbach & Züttel, 2001). Ammonia borane decomposes in three steps at the temperatures of about 100°C, 140°C and 1000°C respectively, releasing one mole equivalent of hydrogen in each step. It was observed that with catalyst, AB starts releasing hydrogen even at room temperature and the induction period was found to be practically absent.
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