Chemical decoupling strategy reveals the distinct contributions of microporous structure and oxygen functionalities to charge storage in porous carbon electrodes

Porous carbons are widely used as electrode materials for electrochemical energy storage; however, the respective contributions of pore architecture and surface oxygen functionalities to charge storage remain difficult to distinguish because these characteristics evolve simultaneously during carbonization. In this work, a systematic chemical-structural decoupling strategy is developed to evaluate and disentangle the effects of pore structure and surface chemistry on the electrochemical performance of porous carbons. Electrochemical kinetic analysis demonstrates that charge storage is predominantly associated with surface-controlled electrical double-layer capacitance (EDLC). Correlation analysis further reveals that electrochemically accessible micropores are a major structural factor contributing to EDLC, whereas structural defects exhibit negligible contributions. Hydrogen reduction is employed to construct a predominantly EDLC-type carbon model, where the strengthened correlation between micropore characteristics and capacitance provides supporting evidence for the dominant role of microporous interfaces, while mesopores mainly facilitate ion transport. Furthermore, selective LiAlH 4 reduction and esterification treatments enable identification of the electrochemically active oxygen species. Carbonyl groups together with a portion of carboxyl groups are found to contribute to pseudocapacitance, whereas hydroxyl groups, ester groups, and overall oxygen content have limited influence on capacitance. Oxygen functionalities also indirectly enhance electrochemical performance by improving electrolyte wettability and micropore accessibility. These findings provide a clearer understanding of the structure-performance relationship in porous carbon electrodes and offer useful guidance for the rational design of high-performance carbon materials for electrochemical energy storage.