Self-Assembled Co₃O₄Nanospheres on N-Doped Reduced Graphene Oxide (Co₃O₄/N-RGO) Bifunctional Electrocatalysts for Cathodic Reduction of CO₂and Anodic Oxidation of Organic Pollutants

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.