Supercapacitive behavior of two-dimensional carbon nanosheets with oxygen-induced interfacial modification

Biomass-derived carbon typically contains abundant heteroatomic defects and interfacial functional groups, which can contribute to additional pseudocapacitance. However, the type of interfacial functional groups in biomass-derived carbon is uncontrollable and variable, reducing their homogeneity. In this work, recyclable boric acid was employed as an activator to convert bioaerogels into carbon nanosheets. Subsequently, low-temperature air oxidation was utilized to modulate their thickness and microstructure. Notably, the multiple and uncontrollable functional groups at the carbon interface were uniformly transformed into oxygen-containing functional groups under oxygen induction, resulting in 2D carbon nanosheet materials with enhanced stability properties. Meanwhile, the introduction of more oxygen-containing functional groups, such as carbonyl (C=O) and carboxyl (-COOH) groups, improves material wettability and capacitive properties. In addition, the boron and nitrogen elements doping introduced by activators and precursors enhances its pseudocapacitive properties and electrical conductivity from the carbon lattice perspective. Moreover, the rich electron/deficient effect of BN valence bond can effectively boost their conductivity and rate performance. In fact, the materials present good capacitive properties (high specific capacitance of 298.5 F g⁻¹ in KOH three-electrode system) and CDI (capacitive deionization) performance (good desalting capacity of 35.2 mg g⁻¹ in CDI system).