Effect of boric acid on thermal dehydrogenation of ammonia borane: H2 yield and process characteristics

Abstract

We have recently demonstrated that boric acid (H3BO3, BA) is a promising additive to decrease onset temperature as well as to enhance hydrogen release kinetics for thermolysis of ammonia borane (NH3BH3, AB). The observations suggest that tetrahydroxyborate ion released by heating BA serves as Lewis acid and catalyzes AB dehydrogenation. Using this approach, we obtained high H2 yield at 85°C, along with rapid kinetics. Various operating conditions were investigated, such as reactor temperature, AB wt %, and particle size of BA. Even in the presence of 10 wt % BA, high H2 yield (13 wt %) and trace amount of ammonia (10-20 ppm) were obtained at 80°C, proton exchange membrane (PEM) fuel cell operating temperature. To our knowledge, such H2 yield value is higher than from any other method using AB with additive or catalyst at PEM fuel cell operating temperatures. © 2013 American Institute of Chemical Engineers.