Amorphous cobalt–copper oxide for upgrading anodic electro-oxidation of glycerol to formate in a basic medium†

Abstract

The electrochemical glycerol oxidation reaction (GOR) offers a dynamically favourable pathway to transform biomass byproducts into value-added chemicals such as formic acid, glycolic acid, glyceraldehyde, and glyceric acid. This approach offers a more efficient utilization of glycerol and might fulfil the anticipated future demands for formic acid, and which serves as a potential fuel for both direct and indirect formic acid fuel cells. However, the current challenge lies in the low oxidation activity and conversion ratio exhibited by existing catalysts. Herein, an amorphous Co₃O₄–CuO/CN_x-300 composite on a carbon cloth was fabricated, which shows high activity toward electrochemical glycerol oxidation with a very low potential of 1.25 V (RHE) at 10 mA cm⁻² and a very high faradaic efficiency of about 91% (formic acid = 81% and glycolic acid = 10%) at 1.5 V (RHE) potential for oxidative product formation with a high selectivity of 89% for formic acid production. Furthermore, the as-prepared Pt/C‖Co₃O₄–CuO/CN_x-300 electrolyzer required 260 mV less potential compared with conventional water splitting to achieve a current density of 10 mA cm⁻². In addition, the electrolyzer was stable at a cell potential of 1.7 V for up to 60 hours, reducing the energy consumption of traditional water splitting by ∼15.48%. The high GOR performance of Co₃O₄–CuO/CN_x-300 is attributed to the synergistic interaction between its components, its amorphous structure, and its high surface area. This study offers fascinating insights for designing cost-effective transition metal-based electrocatalysts, aiming to facilitate glycerol oxidation for the production of value-added chemicals while boosting efficient cathodic hydrogen evolution with minimal energy depletion.