Nickel-based bimetallic nanocatalysts in high-extent dehydrogenation of hydrazine borane

Hydrazine borane N2H4BH3 (HB) is a promising chemical hydrogen storage material but its development is highly dependent on the catalyst that will be used to dehydrogenate it, that is, to hydrolyze the BH3 group and then to decompose selectively the N2H4 moiety into H2 and N2. Finding a reactive and selective catalyst is thus crucial. This is the topic of the present work, where we mainly focused on nickel-based bimetallic nanoparticles synthesized using a hexadecyltrimethylammonium bromide-aided co-reduction method (sodium borohydride or ammonia borane as reducing agent). The second metal, in amounts from 0.03 to 0.23 mol%, was chosen to be ruthenium, rhodium, platinum and iridium. With the 49 nanocatalysts prepared, discrepant results were found; the mol number of H2 + N2 per mol of HB varied from 3.1 to 5.1. The best bimetallic systems were then characterized by XRD, TEM, and XPS. Our main results are reported and discussed herein.

► The dehydrogenation of hydrazine borane N2H4BH3 is a two-step catalytic process. ► The hydrolysis of BH3 occurs first, and is followed by the decomposition of N2H4. ► Bimetallic Ni-noble metal nanoparticles are active in the decomposition of N2H4. ► Up to 5 equiv. N2 + N2 per N2H4BH3 can be released at 50 °C, while some NH3 form. ► One of the most selective bimetallic nanoparticles is Ni0.89Ir0.11.