The coupled activation of microorganism and cobalt salt for the fabrication of biomass-derived carbon materials with superior performance for oxygen reduction reaction

This study innovatively proposes a simple and environmentally friendly method for preparing highly efficient oxygen reduction reaction (ORR) biomass-based electrocatalyst through coupling microorganism pretreatment and cobalt (Co) metal modification. In this work, biomass material was first treated by the microorganisms, which promoted the depolymerization of the cross-linking structure and nitrogen (N) enrichment of the biomass. The depolymerization of the structure can enhance the dispersibility of the Co salt modifier in the precursor, thereby preventing the metal from aggregating into large particles and improving the etching and pore-forming effect of the Co salt modifier during the carbonization process. In addition, utilizing the coordination anchoring effect between N and transition metals, nitrogen enrichment in the precursor derived from microorganism treatment can promote the formation of Co-N coordination structures in the carbon skeleton. Thereby, a carbon catalyst with high-density active sites (Co-N x , Graphite N, and Pyridine N), locally reinforced graphitization and hierarchical porous structure was achieved via the coupling strategy of microorganism pretreatment and cobalt chloride activation. The optimized carbon catalyst demonstrated exceptional electrocatalytic performance, achieving an onset potential of 0.25 V vs. SCE, and a maximum power density of 921 mW m⁻² when integrated into a microbial fuel cell. • Coupled microorganism treatment and CoCl 2 modification for biomass-carbon catalyst. • Microorganism treatment can achieve structure deconstruction and N enrichment. • Coupling strategy can improve the Co dispersion in carbon skeleton. • Achieved high-density Co-N x active sites and hierarchical porous structure. • Enhanced oxygen reduction reaction performance with E onset of 0.25 V vs. SCE.