(259e) Active Role of Carbon Dioxide in the Dehydrogenation of B-N-H Compounds

B-N-H compounds including ammonia borane (AB, NH₃BH₃) and polymeric aminoborane (PAB, (H₂BNH₂) n) are promising on-board hydrogen storage materials. To satisfy the DOE 2017 target (5.5 wt% H₂ based on the total system), about 11 wt% H₂ should be usable from a storage material. Thus, the research challenge is to propose a facile and economical method to extract 11 wt% H₂ from the starting material of AB at the working temperature of fuel cell (80 – 90 ^oC). The present study has found that gaseous CO₂ environments can enhance the dehydrogenation of AB and PAB. After AB is pre-treated at 70 ^oC and with 1.38 MPa of carbon dioxide (CO₂) for 38 min, the rapid hydrogen release of 1.5 moles H₂ per mol of AB was achieved within 1 hour at 85^oC. Furthermore, when PAB, the spent fuel of AB with 0.91 equivalent hydrogen release, was exposed to 2.07Mpa of CO₂ at 85^oC, the rapid hydrogen desorption of 0.84 mol H₂ per mol of AB was observed. The total hydrogen release starting from AB is 11.4 wt% based on an initial mass of AB. For both cases, the degree of dehydrogenation is confirmed by ATR-FTIR spectroscopic and elemental analyses of the thermolytic solid products. Based on the IR, Raman, and elemental analyses of the solid products, we will address a possible mechanism for the enhanced dehydrogenation of AB and PAB in CO₂ environments.