Synergy of cobalt vacancies and iron doping in cobalt selenide to promote oxygen electrode reactions in lithium-oxygen batteries

Electronic structural engineering plays a key role in the design of high-efficiency catalysts. Here, to achieve optimal electronic states, introduction of exotic Fe dopant and Co vacancy into CoSe2 nanosheet (denoted as Fe-CoSe2-V-Co) is presented. The obtained Fe-CoSe2-V-Co demonstrates excellent catalytic activity as compared to CoSe2. Experimental results and density functional theory (DFT) calculations confirm that Fe dopant and Co defects cause significant electron delocalization, which reduces the adsorption energy of LiO2 intermediate on the catalyst surface, thereby obviously improving the electrocatalytic activity of Fe-CoSe2-V-Co towards oxygen redox reactions. Moreover, the synergistic effect between Co vacancy and Fe dopant is able to optimize the microscopic electronic structure of Co ion, further reducing the energy barrier of oxygen electrode reactions on Fe-CoSe2-V-Co. And the lithium-oxygen batteries (LOBs) based on Fe-CoSe2-V-Co electrodes demonstrate a high Coulombic efficiency (CE) of about 72.66%, a large discharge capacity of about 13723 mA h g(-1), and an excellent cycling life of about 1338 h. In general, the electronic structure modulation strategy with the reasonable introduction of vacancy and dopant is expected to inspire the design of highly efficient catalysts for various electrochemical systems. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

Electronic structural engineering, through introduction of exotic dopant and vacancy, enhances the catalytic activity of CoSe2 nanosheets for oxygen redox reactions. Fe dopant and Co defects promote electron delocalization and reduce the adsorption energy of LiO2 intermediate, improving the electrocatalytic activity. The synergistic effect between Co vacancy and Fe dopant optimizes the electronic structure of Co ion and reduces the energy barrier of oxygen electrode reactions. Lithium-oxygen batteries based on Fe-CoSe2-V-Co electrodes exhibit high Coulombic efficiency, large discharge capacity, and excellent cycling life.