N‐Doping‐Induced α‐MnO ₂ /δ‐MnO ₂ for Efficient Glycerol Oxidation to Formic Acid in Acidic Media

ABSTRACT Resource scarcity and environmental pollution have made electrocatalytic water splitting the focus of research. However, the energy‐intensive oxygen evolution reaction (OER) of the anode greatly limits the reaction rate of water splitting. Replacing OER by glycerol oxidation reaction (GOR) not only reduces energy consumption but also produces the value‐added product formic acid. In this work, the mixed‐phase catalyst α‐MnO ₂ /δ‐MnO ₂ (N‐MnO ₂ ) prepared by N‐doping and induced phase transition exhibits excellent GOR performance in acidic media. N‐MnO ₂ requires a low potential of only 1.27 V at 10 mA cm ⁻² , has a superb durability of 100 h, and the Faraday efficiency (FE) of formic acid is as high as 99%. In situ Raman confirmed that the catalyst undergoes a phase transition of α‐MnO ₂ →δ‐MnO ₂ during the GOR process, and that the active phases that really work in GOR and OER are δ‐MnO ₂ and α‐MnO ₂ , respectively. Density functional theory (DFT) calculations reveal that N doping causes the adsorption energy barriers and H transfer energy barriers of glycerol molecules to decrease and the d‐band center level of MnO ₂ to shift downward, which accelerates the reaction. In addition, N‐MnO ₂ showed universal applicability in electrocatalytic oxidation of biomass‐derived polyols, which provides implications for the development of excellent Mn‐based oxide catalysts.