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In this work, a glucose-derived carbon supported CrN composite is prepared by using a hydrothermal method and followed by a nitridating process. It is found that CrN nanoparticles in the composite are well-dispersed and separated by the carbon support. More importantly, the composite exhibits significantly enhanced oxygen reduction reaction activity than free-standing aggregated CrN nanoparticles, especially in acidic medium. The onset potential of the composite reaches 0.81 V in acidic medium, which is one of the highest values among the reported metal nitrides. The rotating ring disk electrode results indicate that the composite is more beneficial to O2 dissociation than free-standing CrN nanoparticles. Results of X-ray photoelectron spectroscopy, O2 temperature-programmed desorption and electrochemical impedance spectroscopy indicate that the significantly enhanced oxygen reduction reaction activity of the composite over free-standing CrN is derived not from the new formed active sites or enhanced oxygen adsorption but from the much enhanced electron transfer rate. This observation helps to understand the role of electron transfer rate playing in the oxygen reduction reaction activity of metal nitrides.

In this study, a novel low-Pt core-shell catalyst is successfully prepared by depositing ultrathin Pt layer on the carbon nanotubes supported titanium nitride nanoparticles (TiN@Pt/CNTs) via a facile pulse electrochemical deposition approach. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), High-angle annular dark field (HAADF) and energy-dispersive spectrometer (EDS) elemental mapping, X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results confirm the core-shell structure of the prepared TiN@Pt/CNTs catalyst. More importantly, the catalyst exhibits superb mass activity and durability for the methanol oxidation reaction (MOR) than that of the commercial JM Pt/C catalyst. Later experiments data demonstrate that the activity and stability of the catalyst can be further enhanced via copper doping, which results from the modified electronic structure of the Pt atoms and the synergistic effects of the core-shell structure.

Core-shell structured Ru@Pd/C catalysts for the electrooxidation of formic acid are synthesized by an organic colloid method associated with a pulse electrodeposition process. The catalysts are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of the catalysts is evaluated by cyclic voltammetry, CO stripping and chronoamperometry technologies. The core-shell structure is revealed by both materials characterization and electrochemical methods, including STEM and energy dispersive X-ray spectroscopy (EDX), the binding energy difference of the XPS spectra and the potential shift of the CO stripping peaks. Such core-shell structured Ru@Pd/C catalysts show excellent activity towards the anodic oxidation of formic acid. The mass activity reaches 5.06 A mg−1Pd and 0.53 A mg−1metal which are ∼10.1 and 1.1 times that of commercial Pd/C. The encouraging performance of Ru@Pd/C is ascribed to the distinct dispersion of the Ru cores and the resulting Ru@Pd nanoparticles as well as the synergy between the core and shell that not only significantly enhances the ability to oxidize the formic acid but also improves the tolerance to CO.