In this work, we present the preparation and characterization of biomass-derived activated carbon (AC) in view of its application as electrode material for electrochemical capacitors. Porous carbons are prepared by pyrolysis of chestnut seeds and subsequent activation of the obtained biochar. We investigate here two activation methods, namely, physical by CO₂ and chemical using KOH. Morphology, structure and specific surface area (SSA) of synthesized activated carbons are investigated by Brunauer-Emmett-Teller (BET) technique and scanning electron microscopy (SEM). Electrochemical studies show a clear dependence between the activation method (influencing porosity and SSA of AC) and electric capacitance values as well as rate capability of investigated electrodes. It is shown that well-developed porosity and high surface area, achieved by the chemical activation process, result in outstanding electrochemical performance of the chestnut-derived porous carbons.

This paper reports on the role of oxidised carbon nanotubes (oxMWCNTs) present in poly-3,4-ethylenedioxytiophene (PEDOT)/graphene oxide (GOx) composite. The final ternary composites (pEDOT/GOx/oxMWCNTs) are synthesised by an electrodeposition process from the suspension-containing monomer, oxidised carbon nanotubes and graphene oxide. Dissociated functional groups on the surface of graphene oxide play a role of counter-ions for the polymer chains. Detailed physicochemical and electrochemical characterisation of the ternary composites is presented in the paper. The results prove that the presence of oxMWCNTs in the ternary composites doubles the capacitance values compared to the binary ones (450 vs. 270 F cm⁻³ for PEDOT/GOx/oxMWCNTs and PEDOT/GOx, respectively). The amount of carbon nanotubes in the synthesis solution is crucial for physicochemical properties of the composites, their adhesion to the electrode substrate and the electrochemical performance.

In response to the growing demand for energy-efficient and sustainable industrial processes, this study investigates the use of gagat—a naturally occurring, coal-like material, as a low-cost and scalable precursor for hard carbon (HC) anodes in sodium-, lithium-, and potassium-ion batteries. HC was synthesized using a one-step, low-temperature pyrolysis process, eliminating the need for chemical purification and improving energy efficiency and environmental friendliness. The resulting gagat-derived HC (GHC) exhibits tunable nanoporosity, governed by the pyrolysis temperature, and incorporates electrochemically active mineral phases that enhance performance. The GHC anodes deliver competitive electrochemical performance and high cycling stability across Na- and Li-ion systems. Due to its abundance, simple processing, and residual minerals that enhance the plateau capacity by ∼43% compared to washed material, gagat shows strong potential for next-generation energy storage.