Self-Assembled Co3O4 Nanospheres on N-Doped Reduced Graphene Oxide (Co3O4/N-RGO) Bifunctional Electrocatalysts for Cathodic Reduction of CO2 and Anodic Oxidation of Organic Pollutants

Abstract

The development of efficient and stable bifunctional electrocatalysts is extremely important and challenging, especially when it comes to simultaneous electroreduction of CO₂ (ECR CO₂) and electro-oxidation of organic dyes. Herein, nanorods of Co₃O₄ that self-assemble into Co₃O₄ nanospheres were anchored on nitrogen-doped reduced graphene oxide (Co₃O₄/N-RGO) frameworks via a hydrothermal method. Thorough physicochemical analysis revealed the small-size crystallites, the inherence of the intersheet network, and the large specific surface area of the Co₃O₄/N-RGO nanocomposites. X-ray photoelectron spectroscopy analysis showed that the N-doped RGO could be involved in the electronic modification of Co atoms, resulting in more Co²⁺ active species on the surface of the Co₃O₄/N-RGO nanocomposite. Electrochemical studies revealed that the Co₃O₄/N-RGO bifunctional electrocatalyst showed structural stability and low interface and charge transfer resistance than that of the Co₃O₄ catalyst. It was found that paired Co₃O₄/N-RGO symmetric electrodes possessed an efficient cathodic reduction of CO₂ with 195 μmol/(L cm²) yield of CH₃OH and faradic efficiency (FE) of 74.8% and an anodic degradation of methylene blue (MB) dye at ?0.7 V versus RHE (a reversible hydrogen electrode) in 1.0 M KOH alkaline solution over 60 min. A possible mechanism for bifunctional electrocatalytic reduction of CO₂ and oxidation of an MB dye is schematically demonstrated. The research study highlights the potential use of Co₃O₄/N-RGO as a bifunctional electrocatalyst in the reduction of atmospheric hazardous wastes and the production of value-added chemicals.