Ceria high aspect ratio nanostructures supported on carbon for hydrogen peroxide electrogeneration

Abstract

Electrochemical advanced oxidative processes (EAOPs) have been shown to be very efficient for the removal of organic pollutants that are not mineralized by conventional effluent treatments. These processes are based on the use of an electrocatalyst and/or photocatalyst for the in situ generation of hydrogen peroxide (H2O2) and hydroxyl radicals (OH), and these species are capable of mineralizing organic pollutants. This work aims evaluate electrocatalysts produced from ceria high aspect ratio nanostructures (CeO2 HARN) supported on black carbon (Vulcan XC-72) in different mass proportions of CeO2 HARN (1%, 2.5%, 4%, 5.5% and 10%) by examining the oxygen reduction reaction (ORR) in alkaline medium (1 mol L−1 NaOH) for the electrogeneration of H2O2. Vulcan XC-72 was used as a support because it has a high surface area, high catalytic activity and low cost. The CeO2 HARN were prepared via a hydrothermal method and were supported on Vulcan XC-72 via an impregnation method. The CeO2 HARN/C-based electrocatalysts were characterized physically by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and contact angle measurements and electrochemically by the rotating ring-disc electrode (RRDE) technique. The results of the electrochemical characterization of the materials indicated a considerable improvement in H2O2 electrogeneration over that of pure Vulcan XC-72, and the electrocatalyst containing 1% CeO2 HARN showed a lower starting potential and transferred 2.1 electrons in the ORR, therefore favoring the 2-electron mechanism and consequently providing a higher rate for H2O2 electrogeneration, which was 95% compared with only 54% for pure Vulcan XC-72. These results show that the CeO2 HARN/C-based electrocatalysts evaluated in this work are promising for in situ H2O2 electrogeneration via EAOPs; in particular, the catalyst containing 1% CeO2 HARN shows more promising results and contains a low metallic oxide load supported on the carbon, increasing its cost-benefit.