Stabilizing Lattice Oxygen to Enable Durable MnO ₂ Electrocatalyst for Simultaneous Acidic Hydrogen Production and Biomass Valorization

Abstract Understanding and steering the stability of earth‐abundant electrocatalysts in acidic medium is essential for proton exchange membrane (PEM) water electrolyzer. Manganese oxide (MnO 2 ) is one of the promising candidates for acidic oxygen evolution reaction (OER), but it still suffers from the overoxidation and the underlying mechanism remains elusive. Here, we observed that lattice oxygen was involved in the OER process on γ‐MnO 2 via Mars‐van‐Krevelen mechanism. Combined with theoretical calculation, we revealed that the release of lattice oxygen lowers the energy barrier of Mn dissolution and compromises the electrode durability. Based on this finding, we propose a strategy to efficiently stabilize lattice oxygen and suppress Mn overoxidation by replacing OER with glucose oxidation to formic acid, which follows a Langmuir–Hinshelwood mechanism. As a result, the durability of γ‐MnO 2 was enhanced by 1100 times, enabling long stability up to 960 hours. Moreover, we demonstrated a production rate of 487.1 mmol h −1 for formic acid and 16.7 L h −1 for H 2 at 40 A in a PEM electrolyzer, providing a sustainable and scalable route for converting water and biomass into valuable chemicals and fuels.