In Situ Sulfidation for Controllable Heterointerface of Cobalt Oxides–Cobalt Sulfides on 3D Porous Carbon Realizing Efficient Rechargeable Liquid-/Solid-State Zn–Air Batteries

Designing and constructing highly efficient bifunctional electrocatalysts for oxygen reduction (ORR) and oxygen evolution (OER) is critical to the development of rechargeable Zn–air batteries. Taking into account the multistep electron-transfer process of oxygen electrocatalytic reactions, it is very desirable to design a suitable construction for electrocatalysts with fantastic electronic transport properties and structural advantages. Herein, we highlight in situ heterointerface engineering and a three-dimensional (3D) porous network structure in preparing the electrocatalysts of N,S-codoped 3D carbon matrix with Co9S8/CoO heterojunction (Co–S–O/NSCN). Systematic characterization and electrochemical experiments confirm that the destabilized charge distribution induced by the Co9S8/CoO heterojunction promotes the fast transfer of electrons during the electrocatalytic process. The well-designed 3D-interconnected network structure composed of 2D nanosheets and in situ-generated 1D carbon nanotubes facilitates the multidimensional electron delivery and reactant migration, along with other additional structural advantages of high surface area and enhanced electronic conductivity. Benefiting from these significant advantages, Co–S–O/NSCN exhibits outstanding oxygen electrocatalytic performance with the ORR half-wave potential of 0.865 V, the OER potential of 1.665 V at 10 mA cm–2 (ORR-OER potential gap of 0.80 V), and extraordinary durability in 0.1 M KOH, outperforming the noble-metal Pt/C catalyst and most of the reported Co-based electrocatalysts. Impressively, both the rechargeable Zn–air batteries using liquid and solid electrolytes, assembled by Co-S-O/NSCN catalysts, show satisfactory performance with low charge–discharge gap and long cycling life. This work highlights the superiority of the heterointerface and advanced structural configuration in oxygen electrochemistry, thus giving some inspiration for the fabrication of significant metal–air cathode electrocatalysts.