Fabrication of Co3O4/P-rGO for electrocatalytic reduction of greenhouse CO2 gas into value-added chemicals in aqueous solution

Abstract

The electrocatalytic reduction of greenhouse CO₂ gas into value-added fuels or chemical feedstocks sustainably addresses energy and environmental crises. However, CO₂ reduction is particularly effective with electrocatalysts, which exhibit distinct functionality at electrode surfaces. In this work, we demonstrate the electrocatalytic reduction of CO₂ using flower-like cobalt oxide (Co₃O₄) synthesized via a hydrothermal method. Co₃O₄ is incorporated into P-doped rGO via ultrasonication to form a hybrid electrocatalyst, thereby enhancing CO₂ reduction efficiency by improving electrode surface functionality. Chemical, morphological, and structural characterization of the synthesized catalyst was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. The electrocatalytic reduction of CO₂ was performed in 0.5 M NaHCO₃ aqueous solution at a pH of 7.5 (CO₂ conditions) in a three-electrode system and applying potential vs. Ag/AgCl (3 M KCl sat.) as the reference electrode, platinum wire as the counter electrode, and the prepared catalyst as a modified graphite working electrode. Chronoamperometry shows CO₂ conversion stability under a constant voltage of −0.62 V (vs. Ag/AgCl) for 2.5 hours. The Co₃O₄ catalyst primarily yields ethanoic acid with 69% faradaic efficiency at a current density of −0.5 mA cm⁻². Additionally, ethanoic acid and propanal are detected for the hybrid flower-like Co₃O₄/P-rGO catalyst, with 58% and 9% faradaic efficiencies at a constant current density of −0.8 mA cm⁻². These results highlight that incorporating Co₃O₄ into the P-rGO improves reduction performance. This can provide a promising platform for synthesizing and fabricating shape-based materials as an electrocatalyst, paving the way for a future powered by renewable, boundless energy and wealth from greenhouse CO₂ gas and other pollutants.