A preliminary oxidation-assisted derivation strategy for biomass to N,O co-doped carbon used in multifunctional capacitor applications

Abstract

Biomass is an ideal carbon source for preparing high-performance carbon materials due to its sustainability and affordability. However, the recalcitrance of lignin in some biomass resources can hinder activation and heteroatom doping during carbonization. Herein, we have explored a convenient strategy that employs NaOH and H₂O₂ to remove most of the lignin and simultaneously activate the remaining biomass components. This pretreatment facilitates the production of porous N and O co-doped carbon materials with enhanced surface area and oxygen content, offering more active sites and improved pseudocapacitive behavior. The optimized N,O-RSC-10 electrode exhibits an impressive specific capacitance of 287 F g⁻¹ at 0.5 A g⁻¹, retaining 60.2% of its initial capacitance under a high current load of 50 A g⁻¹. When applied in zinc-ion hybrid capacitors, the N,O-RSC-10 electrode achieves a high capacity of 207 mA h g⁻¹ at 0.1 A g⁻¹ and exceptional cyclability, maintaining 88% capacity after a 25 000-cycle analysis at 2 A g⁻¹. This excellent capacity is due to the synergistic effect of H⁺ ion insertion/extraction within N,O-RSCs and the reversible formation/decomposition of Zn₄SO₄(OH)₆·5H₂O. This study offers an efficient approach for the activation of biomass and production of a porous heteroatom-doped carbon matrix for promising energy storage.