Enhancing Oxygen Reduction Reaction Catalytic Performance of Biomass-Derived Carbon Materials by Ultrasonication Treatment

Biomass-derived carbon materials have been widely studied as oxygen reduction reaction (ORR) catalysts in recent years, and most directly carbonized materials are still inferior to commercial 20% Pt/C in ORR performance. By ball-milling the carbon powder carbonized by yuba, the interior of carbon particles was exposed, which showed that N content inside carbon particles is higher than that on the surface. Then ultrasonication was employed to refresh the surface of the as-obtained carbon particles to increase C-N-active sites to improve their ORR performance. As a result, the as-treated carbon material was comparable to 20% Pt/C as ORR catalyst in all the key ORR activity parameters (only 7 mV and 16 mV negative shift on onset and half-wave potential, respectively, and 0.28 mA cm −2 at −0.5 V versus Hg/HgO larger in limiting current density). Moreover, the ORR durability and the CO resistance of YUC-850 outperformed that of 20% Pt/C. The detailed experiments indicate that ultrasonication treatment can efficiently exfoliate the small raised material portions of low N content from regular particles to expose more refreshed surface with high N content to improve ORR activity. The subsequent centrifugation collection can remove the small particles to inhibit active site coverage and particle coarsening in service, which leads to further improvement in ORR activity and durability. Ultrasonication of another biomass-derived carbon material also showed significantly improved ORR performance. In conclusion, the application of ultrasonication treatment to biomass-derived carbon materials is proposed to fully promote their ORR activity and durability. The superior ORR performance of the treated carbon materials in this paper also indicates that biomass-derived carbon materials indeed have the potential to serve as redox catalysts in the future. Graphical Abstract