Biocarbon monoliths were obtained from Eucalyptus grandis and the influence of wood anisotropy on the electrical and electrochemical performance as supercapacitor electrodes was studied. They were produced from wood pieces cut along the transversal and longitudinal direction of the tree trunk, followed by pyrolysis and, for some of them, also by activation with CO₂. Monoliths with drilled channels were also obtained. All the monoliths were characterized by SEM, nitrogen adsorption/desorption isotherms, electrical conductivity measurements and electrochemical measurements, the latter in 2M aqueous H₂SO₄ electrolyte. Electrical conductivity and specific capacitance are higher for the transversal carbon monoliths than for the longitudinal ones. The electrical conductivity reaches values up to 27 S cm⁻¹ for the transversal monolith. The specific capacitance reaches values up to 260 F g⁻¹ for the transversal monolith that was activated and drilled. However, the highest volumetric capacitance, of 90 F cm⁻³, is found for the longitudinal monolith that was activated and non-drilled. The energy density and power density, both referred to gravimetric and volumetric magnitudes, reach values as high as 36 Wh kg⁻¹ and 12 Wh L⁻¹, and 2181 W kg⁻¹ and 783 W L⁻¹, respectively. Comparison with a commercial powder activated carbon is provided.

In this study, activated biochar was produced using pilot-scale technologies of fast pyrolysis and activation to create desirable morphology, surface chemistry, and adsorptive properties for application in supercapacitors. First, residues from white birch were converted into biochar by fast pyrolysis (~ 450 °C). Then, physical (using CO₂) or chemical (using KOH) activation was carried out in a homemade pilot-scale furnace at 900 °C. These synthesized materials presented distinct porosity structures: micro-/mesoporous (CO₂ material) and highly microporous (KOH material), reaching surface areas of up to 1700 m² g⁻¹. Electrochemical results showed that KOH-activated biochar had higher specific electrical capacitance in both acidic and neutral electrolytes with a maximum specific capacitance value of 350 and 118 F g⁻¹ at 1 A g⁻¹, respectively; while, for CO₂-activated biochar, the maximum obtained values were 204 and 14 F g⁻¹. The greater proportion of oxygenated and nitrogenated functional groups on the surface of the KOH activated biochar, along with its high surface area (with wider porosity), improved its performance as a supercapacitor electrode. Specifically, the low proportion of ultramicropores was determinant for its better electrochemical behavior, especially in the neutral electrolyte. Indeed, these results are similar to those found in the literature on the electrical capacitance of carbonaceous materials synthesized in a small-scale furnace. Thus, the chemical-activated biochar made from wood residues in pilot-scale furnaces is a promising material for use as electrodes for supercapacitors.