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 m 2 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 x H y PO 4 . 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 x H y PO 4 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.