Janus Hollow Nanofiber with Bi-Functional Oxygen Electrocatalyst for Rechargeable Zn-Air Battery

Abstract

Zn-air battery technologies have attracted ever-increasing attention, while the application is hindered by the sluggish kinetics of the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). In order to explore an efficient method to fabricate the high-performance electrocatalyst via modification of advanced nanostructure, we designed a co-axial electrospinning method with in-situ synthesis and subsequent carbonization to construct three-dimensional (3D) flexible Janus-like electrocatalysts for efficient electrocatalysis. 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 the 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 in an alkaline electrolyte, demonstrating the slow potential gap value of 0.696 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 . Finally, 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 new concept and effective strategy for the rational construction of selective bifunctional materials.

Keywords: Janus structure, Hollow nanofiber, Electrospinning, Metal-organic framework, Zn-air battery, Oxygen electrocatalysts