High-Performance Printed Supercapacitors Based on NaOH-Activated Wood-Derived Carbon: Optimized Porosity and Long-Term Stability in Aqueous Electrolytes

The transition to sustainable energy technologies calls for supercapacitors that are not only efficient but also environmentally responsible. In this work, a step towards solving this challenge is taken by applying a low-temperature NaOH activation strategy to alder-wood-derived carbon. Such process generates an amorphous carbon matrix with thinly-layered sheets of graphene-like domains, facilitating efficient ion-electron transport, as revealed through comprehensive material characterizations. Various carbon structures were obtained by adjusting the alkali-to-carbon ratio and activation temperature wherein the most effective is 3:1 ratio at 600 °C (AWC 3-600). Its combined 2393 m² g⁻¹ surface area and 85.4% microporosity provides a pore architecture that works exceptionally well with aqueous electrolytes. When integrated into printed supercapacitors, it achieves ≈307 F g⁻¹ in NaCl and ≈291 F g⁻¹ in K_xH_yPO₄. Even after 10,000 charge–discharge cycles, the devices retain 95% of their original capacitance, demonstrating long-term stability. The results of this study highlights the strong interactions between the electrolyte and pore structure, where NaCl benefits from the microporous AWC 3-600while K_xH_yPO₄ performs better on the mesoporous structure obtained with an activation process of 4:1 ratio at 700 °C (AWC 4-700). This study shows that low-temperature NaOH activation offers an effective way to engineer biomass-derived carbons with tunable electrochemical behavior.