Low content cerium oxide nanoparticles on carbon for hydrogen peroxide electrosynthesis

Abstract

A comparative study using different proportions of CeO 2/C (4%, 9% and 13% CeO 2) was performed to produce H 2O 2, a reagent used in the oxidation of organic pollutants and in electro-Fenton reactions for the production of the hydroxyl radical (OH ), a strong oxidant agent used in the electrochemical treatment of aqueous wastewater. The CeO 2/C materials were prepared by a modified polymeric precursor method (PPM). X-ray diffraction analysis of the CeO 2/C prepared by the PPM identified two phases, CeO 2 and CeO 2− x . The average size of the crystallites in these materials was close to 7 nm. The kinetics of the oxygen reduction reaction (ORR) were evaluated by the rotating ring-disk electrode technique. The results showed that the 4% CeO 2/C prepared by the PPM was the best composite for the production of H 2O 2 in a 1 mol L −1 NaOH electrolyte solution. For this material, the number of electrons transferred and the H 2O 2 percentage efficiency were 3.1 and 44%, respectively. The ring-current of the 4% CeO 2/C was higher than that of Vulcan carbon, the reference material for H 2O 2 production, which produced 41% H 2O 2 and transferred 3.1 electrons per molecule of oxygen. The overpotential for this reaction on the ceria-based catalyst was substantially lower (approximately 200 mV), demonstrating the higher catalytic performance of this material. Gas diffusion electrodes (GDE) containing the catalyst were used to evaluate the real amount of H 2O 2 produced during exhaustive electrolysis. The 4% CeO 2/C GDE produced 871 mg L −1 of H 2O 2, whereas the Vulcan carbon GDE produced a maximum amount of only 407 mg L −1. Thus, the 4% CeO 2/C electrocatalyst prepared by the PPM is a promising material for H 2O 2 electrogeneration in alkaline media.