Electrothermal Oxidation of Ethylene Glycol Over Co₃O₄

Purely electrocatalytic routes for the selective oxidation of alcohols are often limited by overpotential, mass transport, and kinetics due to multiple proton-coupled electron-transfer steps. We report the electrothermal oxidation of ethylene glycol (EG) over cobalt oxide (Co₃O₄) spinel acting simultaneously as an electrocatalyst and a solid thermocatalyst by integrating enhanced temperature and 15 bar O₂ pressure in alkaline electrolyte at controlled current density. Enhanced EG oxidation was observed with increasing temperature from 30°C to 90°C. Glycolate and formate were the main products, while oxalate was only detected in long-term experiments at lower current densities. Selectivity shifted from formate at low temperature, caused by electrochemical C-C cleavage, to rapid glycolate desorption at increased thermal conditions. The virtual Faradaic efficiencies (vFEs), which are the sum of all charge stored in the reaction products, reached 180% at 90°C, confirming that thermal oxidation by O₂ at high pressure contributes to an additional oxidative electron transfer at the solid-electrolyte interface beyond the applied electrochemical potential. These findings demonstrate that superimposing thermal and electrochemical driving forces boosts performance and enables control over reaction pathways. The approach establishes a conceptual and practical framework toward synergy between electro- and thermocatalytic heterogeneous alcohol oxidation toward sustainable chemical transformations.