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The superabsorbent polymer (SAP) of the disposable diaper, which could serve as a substrate for pathogen growth, was valorized into nanostructured carbon through chemical activation for electrochemical hydrogen storage. The Box-Behnken experimental design was employed to elucidate the effects of activation conditions. Optimization results show that activation temperature and KOH:SAPC molar ratio had a greater impact on the textural and morphological characteristics of the nano-activated carbon. The best electrode material exhibited a surface area of 2552 m2/g, a total pore volume of 1.28 cm³/g, a total micropore volume of 0.871 cm³/g, and a pore size of 1.32 nm. The galvanostatic charge/discharge curves indicate that only higher current densities of 1 and 2 A/g could achieve a faster release of stored hydrogen in approximately 4 min. The best material stored hydrogen mainly through the electric double-layer mechanism, and the specific capacity reached 1878 mAh/g (6.60 wt% of H 2), which ranks among the best-reported hydrogen storage capacities with activated carbon. • Diaper waste was used as a sustainable precursor to prepare activated carbon. • Abundant micropores and high surface area allowed high hydrogen storage capacity. • Higher current density achieved faster release of adsorbed hydrogen atoms. • The mechanism of hydrogen storage is mainly electric double layer. [ABSTRACT FROM AUTHOR]