Biochars are considered as promising materials in energy storage and environmental remediation because of their unique physicochemical properties and low cost. However, the fabrication of multifunctional biochar materials with a well-developed hierarchical porous structure as well as self-doped functionalities via a facile strategy remains a challenge. Herein, we demonstrate a heteroatom-doped porous biochar, prepared by a hydrothermal pretreatment followed by a molten salt activation route. With the creation of a high specific surface area (1501.9 m2/g), a hierarchical porous structure, and the incorporation of oxygen-/nitrogen-functional groups, the as-prepared biochar (BC-24) exhibits great potential for supercapacitor application and organic pollutant elimination. The assembled biochar electrode delivers a specific capacitance of 378 F/g at 0.2 A/g with a good rate capability of 198 F/g at 10 A/g, and excellent cycling stability with 94.5% capacitance retention after 10,000 recycles. Moreover, BC-24 also exhibits superior catalytic activity for phenol degradation through peroxydisulfate (PDS) activation. The phenol (0.2 mM) can be effectively absorbed and then completely degraded within only 25 min over a wide pH range with low catalyst and PDS dosages. More importantly, TOC analysis indicates 81.7% of the phenol is mineralized within 60 min, confirming the effectiveness of the BC-24/PDS system. Quenching experiments and EPR measurements reveal that SO4·- and ·OH as well as 1O2 are involved in the phenol degradation, while the non-radical pathway plays the dominant role. This study provides valuable insights into the preparation of cost-effective carbon materials for supercapacitor application and organic contaminant remediation.
Keywords: biochar; free radicals; non-radical pathway; organic pollutant; peroxydisulfate; supercapacitor.