Correlation between Metal-Support Interaction and the Stability of Platinum Nanoparticles Supported on Heteroatom Doped Mesoporous Carbons for Oxygen Reduction Reaction

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) have been regarded as a key element for the development of sustainable and renewable energy conversion devices, owing to their high efficiency and environmental benignity. In PEMFCs, carbon supported Pt-based catalysts (Pt/C) have shown the best activity, yet they are easily deteriorated via several degradation processes such as Pt particle detachment, Pt dissolution, and/or Ostwald ripening. Therefore, understanding and enhancing the durability of Pt catalysts is one of the major challenges for long-term operation of PEMFC. To improve the stability of Pt/C catalysts, recently, heteroatom-doped carbons have been exploited as support materials. In this work, we investigated the relationship between metal-support interaction and durability of Pt catalysts for the oxygen reduction reaction (ORR). For this purpose, three different types of heteroatom-doped ordered mesoporous carbon (OMC) supports, namely O-doped OMC (O-OMC), N,O-doped OMC (N,O-OMC), and S,O-doped OMC (S,O-OMC), were prepared and Pt nanoparticles were supported on these carbon supports. The interaction between Pt and doped OMC supports was investigated by using atomic force microscopy (AFM). It was revealed that the S,O-OMC exhibited the strongest adhesion with Pt, whereas the N,O-OMC showed the weakest adhesion. X-ray diffraction patterns and X-ray photoelectron spectroscopy corroborated the adhesion results. In accelerated degradation tests for the ORR, Pt/S,O-OMC exhibited the highest durability, followed by Pt/O-OMC and Pt/N,O-OMC. These results suggest that sulfur has the strong adhesive strength with Pt, thereby enhancing the durability, but nitrogen exert less adhesive force with Pt, undermining the durability.