Tailoring Cationic Cobalt Vacancies in Molybdenum–Cobalt\nSelenide Derived from POM@ZIF-67 for Enhanced Electrocatalysis in\nLithium–Oxygen Batteries

Slow\nreaction kinetics during redox reactions limits the utilization\nof the high theoretical energy density of lithium–oxygen batteries\n(LOBs). Vacancy engineering, a potential strategy for modulating active\nsites, is critical in the development of high performance catalysts.\nThis study investigates cobalt vacancies in Mo-CoSe<sub>2</sub> nanoparticles\ncreated by selenization of phosphomolybdic acid (POM) embedded into\nzeolitic imidazolate framework-67 (ZIF-67). The nanomaterial exhibits\nan outstanding electrochemical performance, characterized by high\nspecific capacitance and excellent cycle durability. The LOBs with\ncobalt vacancies in the Mo-CoSe<sub>2</sub> electrode material exhibit\na discharge capacity of 21 836 mAh g<sup>–1</sup> at\na current density of 100 mA g<sup>–1</sup> and exhibit stable\ncycling performance over 194 cycles at 300 mA g<sup>–1</sup>. Additionally, density functional theory (DFT) calculations suggest\nthat the presence of cobalt vacancies increases the distance between\nthe surface selenium atoms and the subsurface cobalt atoms. In addition,\ncobalt vacancies modify the electronic structure of the d-orbitals,\nlowering the energy barriers of the reaction and accelerating the\nreaction kinetics by improving the adsorption of the reactants. The\nresearch introduces a strategy for the rational design of efficient\ncathode materials in LOBs.