In situ growth of N-doped carbon nanotubes in Fe-Nx/Fe2O3/Fe3O4-encapsulated carbon sheets for efficient bifunctional oxygen catalysis

Development of efficient bifunctional oxygen catalysts is of interest for zinc-air batteries (ZABs). However, achieving both highly active and durable oxygen reduction and evolution reactions (ORR/OER) in one catalyst remains challenging. Herein, a composite catalyst (m-Fe/N-[email protected]) integrating N-doped carbon nanotubes (NCNTs) and Fe-Nx/Fe2O3/Fe3O4-encapsulated carbon nanosheets is obtained by in situ growth and interface induction strategy. SiO2 is modified with amine groups to anchor Fe3+ and inhibit Fe3+ reduction, and the resulting Fe2O3/Fe3O4 nanoparticles convert g-C3N4 to NCNTs. m-Fe/[email protected] shows superior activity and stability to commercial Pt/C and RuO2 catalysts in ORR and OER, respectively. The high activity of m-Fe/[email protected] is revealed to mainly derive from Fe-Nx moieties, and the contributions of N-C and Fe2O3/Fe3O4 species are reflected in ORR and OER, respectively. Moreover, the constructed ZABs exhibit a peak power density of 160 mW cm−2 and recyclability. This work provides a new idea for the preparation of bifunctional oxygen catalysts.