Selectively anchoring Pd single atoms on specific sites in defective cobalt oxides for efficient lithium-oxygen batteries

Aprotic Li-O₂ batteries, based on the reversible formation of Li₂O₂ by the reaction between Li metal and oxygen, afford extremely high theoretical energy density. However, the nucleation/delithiation mechanisms of Li₂O₂ remain ambiguous. Therefore, it is an important issue for developing high performance Li-O₂ batteries to construct a catalyst system and deeply understand the catalytic mechanism at the atomic level. Herein, we report a strategy for achieving the site-selectively anchoring of Pd single atoms in oxygen vacancy-rich Co₃O₄ (Pd₁-Co₃O_4−x). Atomic-level characterization techniques unravel that the Pd atoms are preferably incorporated into the tetrahedral site of defective Co₃O₄. Theoretical calculations manifest the obvious charge redistribution induced by the selective-anchored Pd single atom coupled with oxygen vacancies can effectively increase the energy band occupancy of Pd 4d orbitals near the Fermi level, which promotes electron transfer and facilitates the adsorption of intermediates. This dual interaction can not only regulate the nucleation-growth procedures of Li₂O₂ during discharging, but also benefit the delocalization of the electron cloud on Li₂O₂ and weaken the strength of the Li–O bond, which promotes the decomposition of Li₂O₂ during charging. This work proposes some insights into the catalytic mechanism at the atomic level and facilitates the rational design of highly efficient catalysts for Li-O₂ batteries.