Single-Atom Pd-N 4 Catalysis for Stable Low-Overpotential Lithium-Oxygen Battery.

The critical challenge for Li-O 2 batteries lies in the large charge overpotential, leading to undesirable side reactions and inferior cycle stability. Single-atom catalysts have shown promising prospects in expediting the kinetics of oxygen evolution reaction (OER) for Li-O 2 batteries. However, a present practical drawback is the limited understanding of the correlation between the unique atomic structures and the OER mechanism. Herein, a template-assisted strategy is reported to synthesize atomically dispersed Pd anchored on N-doped carbon spheres as cathode catalysts. Benefiting from the well-defined Pd-N 4 moiety, the morphology and distribution of Li 2 O 2 products are distinctly regulated with optimized decomposition reversibility. Theoretical simulations reveal that the unique configuration of Pd-N 4 will contribute to the electron transfer from Pd atoms to the adjacent N atoms, which turns the originally electroneutral Pd into positively charged and downshifts the d-band center and therefore weakens its adsorption energy with the intermediates. The Li-O 2 batteries with Pd SAs/NC cathode achieve a charge overpotential of only 0.24 V and sustainable low-overpotential cycling stability (500 mA g -1 ), and can retain a low charge voltage to a very high capacity of 10 000 mAh g -1 . This work provides some insights into designing efficient single-atom catalysts for stable low-overpotential Li-O 2 batteries.