Electrocatalytic oxidation of methanol at nanoparticle-based MnOx/NiOx/Pt ternary catalysts: Optimization of loading level and order of deposition

Abstract

A nanoparticle-based ternary catalyst composed of Pt (nano-Pt), nickel oxide (nano-NiOx) and manganese oxide (nano-MnOx), all were assembled on a glassy carbon (GC) substrate, was developed for the direct methanol electro-oxidation reaction (MOR) in an alkaline medium. The electrocatalytic activity of the modified electrodes toward MOR depended on the loading level of nano-Pt, nano-NiOx and nano-MnOx onto the GC electrode. Moreover, the order of deposition of nano-NiOx and nano-MnOx has critically influenced the catalytic activity and stability of MOR. The highest electrocatalytic activity was obtained at the MnOx/NiOx/Pt/GC electrode with nano-Pt directly deposited onto the GC surface followed by nano-NiOx and nano-MnOx sequentially. The catalytic activity of MOR at this electrode was about five times higher than that obtained at Pt/GC electrode. The stability and the effect of the operating pH on the catalytic activity of the proposed catalyst were investigated. Several techniques such as the cyclic voltammetry, field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) were used to address the catalytic activity of the catalyst and to reveal its surface morphology and bulk composition.