Metal chloride-doped ammonia borane thermolysis: Positive effect on induction period as well as hydrogen and borazine release

In this work we studied the effect of metal chlorides (CoCl2, FeCl3 and AlCl3) on thermal decomposition of ammonia borane NH3BH3 (AB). The chlorides were chosen because they are simple and cost-effective. They showed promising performances as the onset temperature of AB decomposition decreased. Temperatures of 52, 65 and 85 °C were determined for CoCl2-, FeCl3- and AlCl3-doped AB whereas it was 99 °C for AB. The induction period of AB dehydrogenation has been reduced. The relative mass losses were found as being 11.9, 12.3 and 10.4 wt% at about 110 °C but at 85 °C they were 4.5, 4.5 and 1.6 wt%, respectively. The gaseous side-products were analyzed and traces of borazine B3N3H6 were detected. It was found that the CoCl2 presence has a positive effect on the B3N3H6 evolution. The solid by-products were characterized by XRD and IR: [NH2BH2]x forms after the first decomposition of AB and [BNHx]z forms after the second decomposition. The IR-print of [BNHx]z resembles that of BN, what suggests high dehydrogenation extent. These results are analyzed and discussed in the present paper.