Efficiently Enhanced Selectivity of Electrocatalyzing Ethanol to High Value-Added Acetaldehyde Through Tuning the Cobalt Valence State

Using electrochemical oxidation of alcohols to substitute the oxygen evolution reaction is beneficial to reduce the energy consumption of hydrogen production. Converting alcohols into high value-added products with high efficiency and selectivity by designing a proper electrocatalyst is economical and has promising applications. In this work, two types of spinel cubic phase Co3O4 with different contents of oxygen vacancies were obtained by annealing the same precursor in air and argon gas atmosphere, respectively. The results of X-ray photoelectron spectroscopy and in situ Raman spectra reveal that abundant Co4+ sites were formed on the surface of Co3O4–air under the electrocatalysis condition, while main Co3+ sites were formed on the surface of Co3O4–Ar. The electrocatalytic ethanol oxidation tests and density functional theory calculation reveal that the Co4+ sites exhibit more proper adsorption energy to the O═*CCH3 intermediate, which benefits the formation of high-value-added acetaldehyde products instead of common acetic acid products with a higher degree of oxidation. The Faradaic efficiency of the Co3O4–air catalyst to acetaldehyde achieves 60.02%, and the selectivity to acetaldehyde reaches 79.63% at an oxidation overpotential of 1.46 V. This work provides the possibility and guidance for electrochemical oxidation of alcohols into high value-added products.