A Cellulose Pore Adsorption Strategy to Prepare CoFe/Co8FeS8 Heterostructures into N/S-Doped Carbon Cavities for Enhancing ORR/OER Performance

To address the complex synthesis and metal agglomeration for partially sulfurized heterostructures, a cellulose pore adsorption strategy is proposed to fabricate CoFe/Co8FeS8 heterostructures in N/S-doped biocarbon cavities. In the absence of chelating agents, the porosity and active groups of cellulose enable the preadsorption of metal ions and N/S sources in willow catkin via ion adsorption and hydrogen bonding, respectively. The spatial confinement provided by biopores facilitates incomplete metal sulfuration while effectively preventing metal migration/aggregation. This catalyst demonstrates superior oxygen evolution and reduction reaction performance, with a minimal potential gap of 0.72 V in 0.1 mol·L–1 KOH, exceeding commercial Pt/C+RuO2. When applied in Zn-air batteries, the optimized electrode affords a high specific capacity of 803 mAh·gZn–1 and long-term cycling durability exceeding 500 h. These enhancements are attributed to the self-driven electron transfer between CoFe and Co8FeS8, and from the core to the carbon shell, which induces local electron enrichment at the interface, influencing the adsorption of key reactants. Besides, the ample N/S heteroatoms in the carbon shell further unlock extra active sites, and carbon cavities also inhibit metal nanoparticle shedding during testing, thereby enhancing electrocatalytic stability. This work offers a simple yet effective strategy for designing advanced heterostructure electrocatalysts.