Tuning electronic structure of cobaltous nitride-manganous oxide heterojunction by N-vacancy engineering for optimizing oxygen electrocatalysis activity

Cobalt nitrides (CoN) show excellent catalytic activities due to their distinct electronic structure. However, in general, it is difficult for a single component CoN to achieve the constraint, adsorption and catalysis requirements of Zn-air batteries (ZABs) at the same time. With the advantage of fast charge transfer, heterojunction engineering on a CoN-based catalyst is identified as a viable method to elevate the bifunctional electrocatalytic performance for improving the electrocatalytic performance and application of ZABs. The nitrogen vacancy (VN) engineering of CoN can not only cause lattice strain at the interface to induce electron delocalization, but also regulate the electron density at the interface. Herein, we demonstrate that the electronic density of CoNVN-MnO heterostructure can be effectively regulated for ORR/OER catalysis by vacancy regulation strategy. Different VN concentrations are modeled by theoretical calculations, and the electron localization function confirms that obvious accumulation of electrons on the VN and interfaces between CoNVN and MnO, which contribute to the adsorption and activation of oxygen and reactant molecules and lower thermodynamic barriers for the ORR/OER. The resultant CoNVN-MnO nanocrosses exhibit high power density (171 mW cm−2) for ZABs and remarkable cycling stability with 55 cycles at 2 mA cm−2 for flexible ZABs. [Display omitted] •Introduction of nitrogen vacancies into CoN-MnO heterojunctions by hydrogen reduction.•Modulation of the electronic structure of catalysts by nitrogen vacancy engineering.•The strong synergistic effect between heterojunctions and vacancies for ORR/OER is explored.•N vacancies increase electron density around the Co atom.•In-situ Raman is used to explore the ORR/OER mechanism.