From local wood charcoal to high-performance supercapacitors: The role of pore accessibility

Locally produced wood charcoal was explored as a sustainable and competitive precursor for activated carbon (ACs) applied to advanced energy storage applications. Three different activation strategies were applied: steam activation, KOH activation after physical mixing (KOH-p), and KOH activation after impregnation (KOH-imp). All materials demonstrated good electrochemical performance at low charging rates, achieving specific cell capacitance above 40 F g−1 at 0.5 A g−1 in acidic aqueous electrolyte with the best-performing material demonstrating a remarkable cell capacitance value of 64 F g−1 at 0.5 A g−1 (i.e., a specific electrode capacitance of 257 F g−1) while retaining 85 % and 73 % of its performance at 5 and 40 A g−1, respectively. Moreover, despite comparable BET areas (∼1500 m2 g−1) and microporous volumes (∼0.5 cm3 g−1), ACs produced by KOH-p exhibited restricted micropore accessibility, leading to lower performance at high charging rates. In contrast, ACs with increased pore volume and wider pore size from the AC-KOH-p series retained 73 % of their capacitance, while the KOH-imp series stabilized at 55 %. These findings highlight the critical role of hierarchical porosity and effective micropore accessibility in enhancing charge transport and overall electrochemical performance, reinforcing the value of local biomass sources in the development of sustainable energy storage materials.