Waste wood tar based porous carbon electrodes for supercapacitors with excellent performances through condensation cross-linking modification

Abstract

Wood tar is an unavoidable by-product during a slow-pyrolysis process of biomass, which is usually discarded as a waste and results in environment pollution. Recently, wood tar has been used as a starting material for carbon electrodes because of its thermoplasticity and high carbon content. However, wood tar is mainly composed of various light phenolic molecules, which usually leads to a low carbonization yield after carbonization and an inferior electrochemical performance after activation. In this work, in order to improve the carbonization rate and electrochemical performance of these materials, wood tar was first condensed and crosslinked with formaldehyde and urea via a condensation reaction to produce condensed macromolecular resins, which were then carbonized at 550°C and activated with KOH at 800°C to prepare high-performance nitrogen-doped carbon electrodes for supercapacitors. The samples possess high carbonization yield, large specific surface area (3515.1 m²g⁻¹) and moderate nitrogen content (1.11 %). The high-performance carbon electrodes fabricated by this method achieves a high capacitance of 437.8 F g⁻¹ (6 M KOH electrolyte) at 1 A/g⁻¹. The assembled supercapacitor has an energy density of 13.41 Wh kg⁻¹ at a power density of 124.93 W kg⁻¹. And the capacitance retention was essentially 100 % after 10000 cycles at 5 A g⁻¹. The study presents an innovative strategy for the production of porous carbon for supercapacitors using wood tar and improves carbonization yield via condensation cross-linking modification.