Pt-CeOx/MWCNT electrocatalysts as ethanol-tolerant ORR cathodes for Direct Alcohol Fuel Cells

Abstract

High performance 20% Pt-CeOx (1:1 Pt:Ce weight ratio) electrocatalyst dispersed on Multiwalled Carbon Nanotubes (MWCNTs) was synthesized under H2 atmosphere at 300 °C. The average particle size determined from XRD was ca. 1.7 and 10 nm for Ce and Pt, respectively. HRTEM analysis confirmed the presence of particle sizes within this range, although it was not possible to distinguish Ce from Pt nanoparticles. The XPS spectrum of Ce showed characteristics that indicate the existence of both oxidized and reduced phases (i.e., Ce2O3 and CeO2). It is suggested that the presence of the C3+ state establishes the capacity of this material to act as a tolerant cathode. The spectrum of Pt confirmed the presence of Pt metal. The 20% Pt-CeOx/MWCNT cathode showed high electroactivity for the Oxygen Reduction Reaction (ORR). Moreover, this novel material presented a high degree of tolerance to ethanol. During polarization tests in ethanol-containing solution, the Pt-CeOx/MWCNT cathode showed no peak current density due to the ethanol oxidation reaction (EOR) and the onset potential for the ORR shifted by only 80 mV towards more negative potentials. Thus, the presence of ceria clearly enhanced the electrochemical tolerance of the Pt-based cathode to ethanol.