Controllable Electrocatalytic Synthesis of Aldehydes From Alcohols on Co‐Based Catalysts: A Redox Cycling‐Mediated Indirect Oxidation Mechanism

ABSTRACT The electrocatalytic oxidation of biomass‐derived alcohols offers a green and sustainable route for the preparation of aldehydes, which, however, still faces great challenges such as uncontrollable deep oxidation, preferentially to organic acids, complex and harsh reaction conditions, and the necessitation of high‐cost noble‐metal‐based catalysts. Herein, a Co 3+ /Co 4+ ‐mediated indirect oxidation mechanism has been demonstrated for the controllable and selective oxidation of alcohols to aldehydes under neutral conditions. As a proof‐of‐concept, we successfully developed a CeO 2 /Co 3 O 4 /CC catalyst for oxidizing ethylene glycol to glycolaldehyde dimer, which achieves a favorably high Faradaic efficiency of 94.4% and 99.9% selectivity, even standing out from previously reported noble‐metal‐based catalysts. Detailed mechanistic studies reveal that the reaction is driven by the redox cycling of the Co 3+ /Co 4+ redox couple, and the heterojunction interface between CeO 2 and Co 3 O 4 effectively elevates the Co 3+ content in the catalyst, thereby effectively facilitating active Co 4+ species generation as the rate‐determining step and remarkably enhancing the electrocatalytic alcohol oxidation performance. Overall, the proposed reaction mechanism provides novel insights into the selective oxidation of alcohols to aldehydes under mild conditions and paves the way for the development of a series of non‐noble metal electrocatalysts.