Effect of temperature on the ethanol electrooxidation at PtNirich@PtrichNi/C catalyst in acidic and alkaline media

The understanding of the kinetics of the electrochemical oxidation of ethanol at high temperatures is essential for the optimization of direct ethanol fuel cells. Here, we study the kinetics of the ethanol oxidation reaction between 25 and 65 degrees C using PtNirich@PtrichNi catalysts supported on functionalized carbon, in acid and alkaline solutions. The characterization of the catalysts made by X-ray diffraction, scanning-transmission electron microscopy, energy dispersive X-ray spectrometry, selected area electron diffraction, and cyclic voltammetry suggest the formation of core-shell nanostructures of Ni and Pt, while some nanoparticles can be forming alloys. The CO-stripping study reveals that the COads oxidation shifts to negative potentials when the temperature increases, in both 0.5 M H2SO4 and 0.5 M KOH media. However, in alkaline electrolyte, the lower current density at higher temperatures is associated with the COads oxidation. Similar behavior is observed for ethanol oxidation reaction until a temperature of 65 degrees C. The activation energy values calculated by linear sweep voltammetry are 16.28-14.54 kJ mol(-1) in acidic media and 9.25-7.97 kJ mol(-1) in alkaline media. Therefore, the understanding of the kinetics of the ethanol oxidation in the conditions and catalysts studied here could help in selecting the catalytic components and operating environment, which result in enhanced efficiencies toward both COad and ethanol oxidation. (C) 2019 Elsevier B.V. All rights reserved.