Solar-driven synthesis of activated carbons: Thermochemical control of structure, surface chemistry, and electrochemical performance in hybrid supercapacitors

This study investigates the influence of thermochemical processing on the structure and functional properties of activated carbons (ACs) derived from lignocellulosic biomass using a sustainable solar-driven route. Carbons synthesized at 600, 800, and 950 °C were systematically analyzed to establish correlations between thermal treatment, porosity development, surface chemistry, and degree of graphitic ordering. XPS analysis revealed the presence of nitrogen (N ox , N g , N 5 , N 6 ) and oxygen (C O, O-C-N, O-C=O) functional groups, which contribute to redox activity, while BET measurements showed that increasing temperature enhanced the specific surface area up to 1263 m 2 g −1 . However, the carbon obtained at 600 °C (856 m 2 g −1 ) exhibited an optimal balance between porosity and surface functionality. When assembled as anodes in hybrid supercapacitors with a Ni Co MOF cathode, the data indicate that carbon structural ordering and surface chemistry strongly influence the accessible electrochemical potential window and charge-storage mechanisms. An assembled device reached a 1.5 V window and delivered 31.2 Whkg −1 with Coulombic efficiency near 99% and energy efficiency of 85% under the reported test conditions. The emphasis of this work is mechanistic, establishing temperature-dependent structure-property-function correlations that explain how porosity, surface oxygen-containing groups, and graphitic domains govern capacitance, voltage limits, and kinetics in hybrid configurations. These insights provide guidance for tailoring carbon electrodes, while acknowledging that further durability optimization is required for practical deployment.