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High Resolution Transmission Electron Microscopy (HR TEM) is used to identify the size, shape, and interface structure of platinum nanoparticles and carbon support of a fuel cell catalyst. Using these insights, models accessible to quantum chemical methods are designed in order to rationalize the observed features. Thus, basal plane and prism face models of the carbon black material are considered, interacting with Pt clusters of sizes up to 1 nm. Particular attention is paid to the electronic structure of the carbon support, namely, the radical character of graphene zig-zag edges. The results show that a stronger interaction is found when the nanoparticle is at the zig-zag edge of a basal plane due to the combination of dispersion interaction with the support structure and covalent interaction with carbon atoms at the edge. In this case, a distortion of both the Pt nanoparticle and the carbon support is observed, which corresponds to the observations from the HR TEM investigation. Furthermore, the analysis of the charge transfer upon interaction and the influence of the potential on the charge states and structure is carried out on our model systems. In all cases, a clear charge transfer is observed from the carbon support to the Pt nanoparticle. Finally, we show that changing the potential not only can change the charge state of the system but can also affect the nature of the interaction between Pt nanoparticles and carbon supports. [ABSTRACT FROM AUTHOR]

Hollow graphitic carbon nanoparticles (HGCNs) obtained by catalytic graphitization of acetylene carbon black (ACB) were investigated using ultra-soft X-ray emission spectroscopy. The electronic structures of the ACB HGCNs were compared with those of HGCNs obtained from iron carbide-filled carbon nanocapsules (Fe3C@CNCs) and Q-graphenes. The occupation of the π sub-band decreased in the following sequence: Fe3C@CNC HGCNs > ACB HGCNs > Q-graphenes. This sequence can be explained by changes in the occupations of the C2p states due to the formation of bonds between carbon and residual metal atoms within the HGCNs. It was also found that the contribution of the overlapping ofppπ+ppσ-states in the ACB HGCN walls toward the spectra of the HGNCs was greater in comparison with the reference Q-graphenes. It was established that ACB was not fully transformed into the HGCNs. Scanning and transmission electron microscopy methods were used to study the spatial structures and morphologies of the fabricated HGCNs. [ABSTRACT FROM PUBLISHER]