Deposition of Fe-Ni nanoparticles on polyethyleneimine-decorated graphene oxide and application in catalytic dehydrogenation of ammonia borane

Ammonia borane (AB) is one of the most promising hydrogen storage materials due to its high hydrogen content and outstanding environmental stability and non-toxicity, which has stimulated substantial effort devoted to developing highly efficient dehydrogenation catalysts. Transition metal nanoparticles (NPs) such as iron (Fe) and nickel (Ni) are quite attractive due to their advantages in cost, catalytic activity and recycling capability. However, their magnetism and strong aggregation propensity make it a challenge to develop them into highly efficient dehydrogenation catalysts. We propose a method to resolve this issue, in which a weak, branched polyelectrolyte, polyethyleneimine (PEI), is utilized to assist the deposition of Fe-Ni NPs on graphene oxide (GO). These Fe-Ni NPs are prepared by a simple co-reduction method of metal precursors with sodium borohydride under ambient conditions. The content of PEI attached on GO significantly affects the morphology and size of resulting Fe-Ni NPs. For the high PEI content, where most of metal ions are confined within the PEI layer attached on GO, the homogeneous nucleation and growth in the bulk solution are suppressed so that small, amorphous Fe-Ni NPs (similar to 3 nm in diameter) are formed. Compared to the Fe-Ni NPs directly deposited on GO, these NPs on PEI-decorated GO reveal a dehydrogenation rate of 982 ml min(-1) g(-1) at 293 K for the hydrolysis of AB, which is 18 times faster than that of the former and nearly comparable to that of the platinum catalyst deposited on carbon under the same conditions.