Activated carbon materials derived from liquefied bark-phenol formaldehyde resins for high performance supercapacitors

Abstract

Bark phenolic compounds have been used to partially substitute petroleum-based phenol in a resin synthesis due to their similarity. In this work, phenol-liquefied bark-phenol formaldehyde (PF) resins are first used as carbon precursors, and are transformed into activated carbon materials via a KOH activation method. The bark-PF resin based carbons were systematically characterized by scanning and transmitting electron microscopy, N₂ adsorption/desorption, X-ray diffraction, Raman spectra, energy dispersive spectra and X-ray photoelectron spectra. The prepared carbons possess a large surface area and a hierarchical porosity composed of ultramicropores (<0.7 nm), supermicropores (0.7–2 nm) and small-sized mesopores (2–5 nm). As the mass ratio of KOH to bark-PF resin is 2, the activated carbon (BRC-2) shows a highest specific capacitance of up to 370 F g⁻¹ and 251 F g⁻¹ at 0.1 A g⁻¹ and 10 A g⁻¹ in KOH electrolyte, respectively. These values are much higher than many biomass-based carbon materials reported previously. The excellent capacitive performance of BRC-2 may be due to the synergistic effect of electrical double layer (EDL) capacitance and additional pseudo-capacitance. Herein, EDL capacitance is relevant to the accessible surface area to ions of electrolyte, whereas pseudo-capacitance relies directly on the content of basic O groups (phenolic hydroxyl and quinine typed O) and oxidized S groups (sulfone or sulfoxide). The results reported in this work show that bark-based resins could be used to prepare high performance carbon materials for supercapacitors.