Hydrothermal Carbon Coating Enables Enhanced Proton Storage in MoO ₃ via Activated Water Confinement and Oxygen Vacancies

Proton batteries are critically limited by corrosion of transition metal oxide electrodes in acidic electrolytes, a challenge further aggravated by activated water generated during the hydrated proton desolvation. Managing interfacial activated water by spatially separating protons and activated water is therefore essential for stable and efficient proton storage. Here, hydrothermal carbon (HTC) is introduced onto MoO 3 via a facile hydrothermal carbonization of glucose. The resulting HTC coating effectively shields the electrode from direct exposure to acidic electrolytes, promotes hydrated proton desolvation, and confines activated water at the interface. Simultaneously, the hydrothermal carbonization induces oxygen vacancies in MoO 3 (Ov‐MoO 3 @C), modulating the electronic structure and facilitating proton intercalation. Owing to the synergistic effects of activated water confinement and oxygen‐vacancy introduction, the HTC coating enables efficient spatial separation of protons and active water. Consequently, the Ov‐MoO 3 @C electrode exhibits a 11% enhancement in capacity and a 55% improvement in cycling stability compared with pristine MoO 3 . This work highlights hydrothermal carbonization as a dual‐functional strategy for regulating proton transfer and modulating electronic structure, offering a promising pathway toward high‐performance proton batteries.