Janus Hollow Nanofiber with Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Battery.

Zn-air battery technologies have received increasing attention, while the application is hindered by the sluggish kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In order to explore an efficient method to fabricate a high-performance electrocatalyst via modification of advanced nanostructure, a coaxial electrospinning method with in-situ synthesis and subsequent carbonization to construct 3D flexible Janus-like electrocatalysts is developed. The resulting Janus nanofibers have a unique core-shell hollow fiber structure, where NiFe alloy electrocatalysts supported by N-doped carbon nanobelt are located on the inner wall of the carbon layer, and leaf-like Co-N nanosheets are anchored on the outer wall of the carbon layer. As a result, the electrocatalyst exhibits excellent bifunctional catalytic performance for ORR and OER, demonstrating the small potential gap value of 0.73 V between the ORR half-wave potential and the OER potential at 10 mA cm -2 , which is even comparable to the mixed commercial noble catalyst with 20% Pt/C and RuO 2 . The rechargeable Zn-air battery is constructed and displays a large open-circuit voltage of 1.44 V, high power density (130 mW cm -2 ) and energy density (874 Wh kg -1 ). This study provides a concept to synthesize and construct high performance bifunctional electrocatalysts.