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In this research, we successfully produced hierarchical porous activated carbon from biowaste employing one-step KOH activation and applied as ultrahigh-performance supercapacitor electrode materials. The coconut shell-derived activated carbon (CSAC) features a hierarchical porous structure in a honeycomb-like morphology, leading to a high specific surface area (2228 m2 g−1) as well as a significant pore volume (1.07 cm3 g−1). The initial test with the CSAC electrode, conducted in a 6 M KOH loaded symmetric supercapacitor, demonstrated an ultrahigh capacitance of 367 F g−1 at a current density of 0.2 A g−1 together with 92.09% retention after 10,000 cycles at 10 A g−1. More impressively, the zinc–ion hybrid supercapacitor using CSAC as a cathode achieves a high-rate capability (153 mAh g−1 at 0.2 A g−1 and 75 mAh g−1 at 10 A g−1), high energy density (134.9 Wh kg−1 at 175 W kg−1), as well as exceptional cycling stability (93.81% capacity retention after 10,000 cycles at 10 A g−1). Such work thus illuminates a new pathway for converting biowaste-derived carbons into materials for ultrahigh-performance energy storge applications. [ABSTRACT FROM AUTHOR]

A gray TiO₂/SrTiO₃ composite nanocrystalline sensor with narrow band-gap was successfully prepared through a facile wet chemical method. The precursor was calcined in N₂ flow under atmospheric pressure and thereafter, a humidity sensor based on the composite was fabricated. The sensor showed high resistive sensitivity and varied by more than four orders of magnitude with an increase in relative humidity (RH) from 11% to 95%. The response and recovery time were about 3.1 s and 76 s, respectively with maximum hysteresis at 1% RH. In comparison with pure SrTiO₃ and black TiO₂, the gray composite based device exhibits a higher sensitivity. These results demonstrate the potential of gray TiO₂/SrTiO₃ for humidity sensing applications., Competing Interests: The authors declare no conflict of interest.