Investigation of the oxygen reduction kinetics and mechanism on ordered mesoporous carbon-supported Pt-based catalysts

Authors: SİLVER GÜNEŞ, FATMA ÇİĞDEM GÜLDÜR

Abstract: The kinetics and mechanism of oxygen reduction reaction (ORR) on the surface of Pt and PtAgFe catalysts supported by ordered mesoporous carbon (OMC) were investigated. Metal particles were loaded by the wet impregnation-reduction method on two types of OMC, one being surface-modified by HNO₃ and the other unmodified. Cyclic voltammetry measurements showed that Pt on modified OMC, namely Pt/OMC-M, had the highest electroactive surface area among OMC-supported catalyts with 987 cm²/mg. This catalyst had also a mass activity of 39.1 mA/mg_Pt, which was the same as the carbon black supported commercial Pt/C catalyst. Rotating disk electrode (RDE) studies revealed that the net number of transferred electrons for OMC supported Pt and PtAgFe catalysts were in the range between 3 and 4, indicating a predominant 4-electron water formation route. The ORR mechanisms on Pt/OMC and PtAgFe/ OMC were found to be similar with that of Pt/C; however, the associative mechanism was pronounced at a wider potential range. The modified OMC-supported catalysts showed higher oxygen reduction activities in general.

Keywords: Oxygen reduction reaction, reaction mechanism, ordered mesoporous carbon, rotating disk voltammetry

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