Co3O4/CeO2/C As Electrocatalyst for Ethylene Glycol Oxidation Reaction

Abstract

In recent decades, alkaline direct alcohol fuel cells have been interested due to their advantages over hydrogen fuel cell. Alcohols such as methanol and ethanol are the most common types of fuel used in direct liquid-feed fuel cells however alternative alcohols are increasingly being investigated. One of the choices for alkaline alcohol fuel cell is ethylene glycol. Ethylene glycol in an alkaline medium generates, as intermediates, oxalates, glyoxylate, glycolate, glycolaldehyde, glyoxal and carbon dioxide and it is considered an energy carrier for fuel cells. The importance of this fuel is attributed to several factors: low molecular weight, biomass origin, high energy density, high boiling point and lower toxicity than methanol.One more challenge is to find the most efficient electrocatalysts for various fuel oxidation reaction which could replace platinum in fuel cell anode materials in relation to its limited resources and high price.Lately, the most research is based on the development of different, new, rare earth metals and metal oxides compositions, the improvement of known materials such as carbon with various additives with the aim to reduce or completely refuse of noble metal and to find low cost, higher efficient and great performance catalysts.In this study, the Co3O4 was deposited onto the CeO2/C substrates prepared by two different ways. The substrates were prepared as follow: a) dry powder of CeO2 was mixed with carbon powder (mass ratio being 1:1) in a 2-propanol solution by ultrasonication for 30 min with further drying of the mixture (CeO2/C-1); b) CeCO3 were precipitated onto the carbon surface using the appropriate concentrations of CeCl3 and Na2CO3 solutions with stirring on a magnetic stirrer, followed by drying the mixture (CeO2/C-2). Then Co3O4 was deposited onto the CeO2/C-1 and CeO2/C-2 substrates using microwave irradiation and β–cyclodextrin as reducing agent. The synthesized Co3O4/CeO2/C-1 and Co3O4/CeO2/C-2 catalysts were characterized by Inductively Coupled Plasma Optical Emission Spectroscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Diffraction. Electrocatalytic activity of the prepared catalysts was evaluated towards ethylene glycol oxidation reaction in an alkaline medium using cyclic voltammetry and chrono-techniques.It has been found, that the Co3O4 supported catalysts showed higher electrocatalytic activity for the ethylene glycol oxidation reaction than the pure CeO2/C substrates. Moreover, the preparation way of the substrate has had the influence on the electrocatalytic activity of prepared catalysts. It has been found that Co3O4/CeO2/C-2 catalyst where CeO2/C substrate was obtained from CeCl3 salt solution showed higher electrocatalytic activity towards ethylene glycol oxidation reaction than Co3O4/CeO2/C-1 catalyst where CeO2 was directly mixed with carbon powder.