Spherical Core–Shell Titanium (Oxy)nitride@Nitrided Carbon Composites as Catalysts for the Oxygen Reduction Reaction: Synthesis and Electrocatalytic Performance

Abstract

AbstractAiming at the development of highly active and stable platinum‐free catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs), we explored the potential of a new composite material, where the core–shell structure should result in a combination of high ORR activity and improved electric conductivity. TiOxNy@CnNm composite nanoparticles were prepared by covering uniform carbon spheres of about 300 nm in size, synthesized through the hydrothermal reaction of glucose, with a homogeneous titania shell made by sol‐gel processing. The core–shell particles were then subjected to nitridation in ammonia vapor at different temperatures (550 °C–150 °C). The influence of the nitridation temperature on the structure and phase composition of the resulting composite particles was evaluated by a variety of techniques, including electron microscopy (SEM, TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), elemental analysis, thermogravimetric (TG) analysis, and N2 sorption measurements, the electrochemical properties and the ORR performance of the materials were determined by rotating ring disk electrode (RRDE) measurements. Trends in the evolution of the structural/chemical properties and electrochemical/electrocatalytic properties as well as correlations between them are discussed; an optimized mesoporosity of the titanium (oxy)nitride shell was identified as the key criterion for the catalyst's ORR performance.