Pitch-based carbon featuring hierarchical pore sieving and abundant N/O sites for synergistically boosted Zn-ion desolvation kinetics.

Abstract

The kinetics of aqueous zinc-ion hybrid capacitors (ZIHCs) are critically governed by the desolvation behavior of hydrated Zn2+ at the electrode-electrolyte interface, yet simultaneously achieving high active site density and fast ion transport remains challenging. Herein, we report a molecular-scale design strategy to construct N/O co-doped porous carbons (N-CETP-X) from low-cost ethylene tar pitch via pre‑carbonization, oxidative functionalization, and KOH activation. Pre‑carbonization establishes a robust carbon framework, while HNO3 oxidation precisely grafts N/O functionalities, thereby lowering the energy barrier for subsequent activation. Notably, the optimized N-CETP-3 features an ultrahigh specific surface area (3097.6 m2 g-1) and hierarchically interconnected micro/mesopores (0.64-3 nm). This architecture not only provides confined nanospaces for interfacial Zn2+ adsorption but also creates a size-exclusion effect that mechanically strips the hydration sheath. In situ Raman spectroscopy reveals the reversible evolution of D and G bands during cycling, confirming that N/O mediated defects act as stable anchoring sites without degrading the carbon skeleton. Scanning vibrating electrode technique (SVET) further identifies built-in electric fields arising from modulated local electron density, which expedite interfacial charge transfer and lower the desolvation energy barrier. Consequently, the Zn//N-CETP-3 device delivers a remarkable specific capacitance (436.7 F g-1 at 0.2 A g-1), a high energy density (155.3 Wh kg-1), and exceptional cycling durability (98.36% retention after 45,000 cycles at 10 A g-1). This work elucidates the pivotal role of pore-ion size matching and heteroatom-induced charge redistribution in steering desolvation chemistry, offering a fundamental paradigm for designing high-performance carbon cathodes.