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

Abstract

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·g_Zn^–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.