Surface tuning of carbon supported chemically ordered nanoparticles for promoting their catalysis toward the oxygen reduction reaction

The surface microstructure plays a key role in affecting the catalytic performances of platinum (Pt) base nanomaterials used for the oxygen reduction reaction (ORR) catalysts in fuel cell. In this work, carbon supported chemically ordered PtFe nanoparticles (PtFe/C) with small average particle size (similar to 5 nm) were effectively synthesized via a microwave-assisted polyol reduction process and followed by heat treatment. Then, the PtFe/C catalyst was surface doped with small amounts of transition metal Au and Cr. The structural characteristics of the as-synthesized catalysts were characterized by X-ray diffraction, transmission electron microscopy, inductively coupled plasma-atomic emission spectroscopy, X-ray photoelectron spectrometer, and energy dispersive spectrometer in association with high-angle annular dark field scanning transmission electron microscopy; the electrochemical performances were tested by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode. The mass activities of the as-synthesized catalysts toward the ORR increased in the order of PtFe/C (314 mA mg(-1) (Pt)) < Au-PtFe/C (414 mA mg(-1) (Pt)) < Cr-PtFe/C (487 mA mg(-1) (Pt)); all the as-synthesized catalysts showed higher mass activity than that (158 mA mg(-1) (Pt)) of JM Pt/C catalyst. Moreover, Au-PtFe/C and Cr-PtFe/C catalysts showed higher stability than JM Pt/C catalyst. The superior catalytic performances of these doped catalysts were attributed to the chemically ordered structure and the modified surface electric properties. (C) 2017 Published by Elsevier Ltd.