Silver Doping Mediated Route to Bimetallically Doped Carbon Spheres with Controllable Nanoparticle Distributions

We report a facile and efficient approach to prepare bimetallically doped Ag−M−carbon composites. Only if Ag nanoparticles (NPs) are embedded first into the submicrometer carbon spheres (CSs) can the second metal M (Pd, Pt, and Au) also be introduced into their interior. Especially at not too high concentrations of M-precursor ions (CM-ion), the locations and number density of the resulting NPs mirror those of the Ag NPs in/on the CSs. Therefore, the controllability of the Ag predoping allows control over the location dependent distribution of the NPs in the resulting bimetallic composites. The size and shape of the resulting NPs in the composites are largely controlled by the concentration CM-ion. The different shapes include solid core−shell and hollow NPs, as well as hedgehog-like hollow structures and dendritic aggregates. The nucleation and growth mechanisms, which differ between the different metals M, are discussed to explain the morphologies and the location dependence of the NPs in/on the CSs.