A self-supported bifunctional air cathode composed of Co3O4/Fe2O3 nanoparticles embedded in nanosheet arrays grafted onto carbon nanofibers for secondary zinc-air batteries

Secondary zinc-air batteries (ZABs) with a free-standing and flexible air electrode integrated with distinguished bifunctional oxygen electrocatalysts are crucial for achieving better performance. Herein, benefitting from the rational design and simple synthesis, a highly controlled design can be achieved for the first showing of the synthesis of Co 3 O 4 /Fe 2 O 3 NAs@CNFs with a unique hierarchical nanostructure , consisting of randomly distributed zero-dimensional (0D) Co 3 O 4 /Fe 2 O 3 nanoparticles embedded in two-dimensional (2D) MOF derived nitrogen-doped mesoporous carbon flake nanoarrays grown on three-dimensional (3D) microporous network with interconnected conductive one-dimensional (1D) carbon nanofibers from carbonized electrospinning polymer nanofiber film (PMNFs). Under the synergy of 3D hierarchical porous nanostructure and abundant accessible active sites, Co 3 O 4 /Fe 2 O 3 NAs@CNFs is endowed with excellent bifunctional electrocatalytic activities like those of commercial Pt/C and RuO 2 , respectively. Rechargeable aqueous ZABs based on Co 3 O 4 /Fe 2 O 3 NAs@CNFs as air electrodes outperform their counterparts based on Pt/C and RuO 2 loaded carbon nanofibers (CNFs) as air electrodes, with a maximum power density of 246 mW cm −2 and excellent cycling stability with no increased polarization even after 40 h. And the assembled flexible solid-state ZABs with Co 3 O 4 /Fe 2 O 3 NAs@CNFs also display superior performance and bendability.