Rational Design of Ultra-Stable FeS₂-Fe₂N/SN-CNTs Heterostructures with Improved Bifunctional Catalytic Activities...

Zinc-air batteries are considered one of the most promising batteries for energy storage owing to their low cost, high safety, and high energy density. Developing effective bifunctional electrocatalysts is one of the important issues for zinc-air batteries. Although Fe₂N demonstrates oxygen reduction activity comparable to that of Pt-based catalysts, its relatively poor catalytic activity for oxygen evolution and limited exposure of active sites still restrict its application. Herein, we report on the rational design and synthesis of FeS₂ and Fe₂N nanostructures on sulfur- and nitrogen-codoped carbon nanotubes as effective and ultrastable bifunctional electrocatalysts. The highly dispersed FeS₂ and Fe₂N nanostructures on CNTs provide numerous active catalytic sites, and the introduction of FeS₂ improves the electronic structure and charge distribution of the electrocatalysts, significantly reducing the Gibbs free energy for rate-determining steps in the oxygen evolution reaction. The carbon nanotubes here can also accelerate the transportation of electrons and oxygen molecules, as well as enhance the stability of the electrocatalysts. Consequently, it achieved impressive oxygen reduction activity with a half-wave potential of 0.765 V vs RHE and a low overpotential of 0.46 V for the oxygen evolution reaction at a current density of 10 mA cm^-2, respectively. Moreover, the homemade zinc-air battery based on the FeS₂-Fe₂N/SN-CNTs air-cathode can deliver a maximum power density of 119.2 mW cm^-2. This study introduces a novel approach to the design of dual-function catalysts and zinc-air batteries.