KOH-Activated Hierarchical Porous Carbon Derived from Suaeda salsa for Supercapacitor Electrodes: Pore-Structure Evolution and Electrochemical Behavior

The increasing demand for sustainable electrochemical energy-storage materials has stimulated considerable interest in biomass-derived porous carbons. In this study, hierarchical porous carbon was prepared from Suaeda salsa, a renewable halophytic biomass, through thermal pretreatment, carbonization, and KOH activation. The effects of thermal treatment and KOH activation on the pore structure, morphology, surface characteristics, and electrochemical behavior of the resulting carbons were systematically investigated. The results demonstrate that moderate KOH activation substantially opens the carbon framework and promotes the development of accessible porosity while retaining a finite meso/macro-pore network that can facilitate electrolyte transport. Among the investigated conditions, the intermediate activation level provided the most favorable balance between micropore generation, transport accessibility, and framework preservation, leading to the best electrochemical response. The combined structural and electrochemical analyses establish a clear processing–pore structure–property relationship and indicate that electrochemical performance cannot be optimized simply by increasing activation severity. Instead, rational control of hierarchical porosity is important for achieving effective charge storage and ion transport in biomass-derived carbon electrodes. The study provides a sustainable route for converting coastal halophytic biomass into functional porous carbon materials for electrochemical energy-storage applications.