ZIF-derived “senbei”-like Co 9 S 8 /CeO 2 /Co heterostructural nitrogen-doped carbon nanosheets as bifunctional oxygen electrocatalysts for Zn-air batteries

The rational design and construction of the efficient and robust non-noble metal bifunctional oxygen electrocatalysts is of critical significance due to the attention given to reversible metal-air batteries. In this paper, we report novel two-dimensional "senbei"-like Co9S8/CeO2/Co-NC nitrogen-doped carbon nanosheets (Co9S8/CeO2/Co-NC) derived from a unique 2D Co/Ce bimetallic ZIF. The phase transition from 3D spherical Co-ZIF to 2D Co/Ce-ZIF was achieved through the introduction of Ce ions. Profiting from the successful construction of the unique Co9S8/CeO2 heterostructure and the synergetic effect of two components, the as-prepared Co9S8/CeO2/Co-NC exhibited excellent electro-performance in both the oxygen evolution reaction (Ej=10 = 1.60 V) and oxygen reduction reaction (E1/2 = 0.875 V). Furthermore, when used as a bifunctional air electrode for Zn-air batteries, Co9S8/CeO2/Co-NC reached a high peak power density of ≈164.24 mW cm-2 at a high current density of ≈351 mA cm-2 and displayed an outstanding cycling stability of more than 668 h at 5 mA cm-2. This research provides new guidelines for preparing hybrid materials from cobalt-based sulfide species and CeO2 for electrocatalysis and energy storage or other fields.