Composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles having an average size of 1.7 nm for hydrolytic dehydrogenation of ammonia borane

We investigated composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles (DENs) that had a uniform size of ∼1.7nm for hydrolytic dehydrogenation of ammonia borane (AB). The PtPd DENs, composed of seven different Pt: Pd ratios, were synthesized using hydroxyl-terminated sixth-generation polyamidoamine dendrimers as a molecular template. The dendrimer-templating method allowed for synthesizing bimetallic PtPd DENs with controllable nanoparticle composition while fixing the size of the nanoparticles uniformly at ∼1.7 nm. Compared with monometallic Pt and Pd DENs, the bimetallic PtPd DENs showed superior catalytic activity for the hydrolytic dehydrogenation of AB. Furthermore, the bimetallic PtPd DENs exhibited composition-dependent activity with the maximum activity (i.e., average turnover frequency=108.5±15.9mol_H2·mol_{atom Pt+}pd−1·min⁻¹) at a Pt: Pd ratio of 1:1 for the catalytic hydrolysis of AB.