Oxygen-Induced Surface Reconstruction Tunes MoS2 Activity in Li–O2 Electrocatalysis

Rechargeable lithium–oxygen (Li–O2) batteries suffer from large overpotentials in the oxygen reduction and evolution reactions (ORR/OER), which are strongly influenced by the cathode surface structure. Here, density functional theory (DFT) combined with ab initio thermodynamics is used to investigate oxygen-induced reconstruction of MoS2 basal planes and edge sites across the 2H, 1T, and 1T′ phases. Surface phase diagrams show that oxygen substitution is thermodynamically favorable relative to oxygen adsorption and sulfur-vacancy formation for the investigated surfaces under oxidizing conditions, although the driving force depends on the phase and local coordination. The 2H basal plane and sulfur-passivated 2H edges exhibit a weaker driving force for oxygen incorporation, whereas partially desulfurized edges and metallic phases show more favorable oxygen substitution. All investigated surfaces favor Li2O2 formation over Li2O formation, irrespective of phase and oxygen substitution. Oxygen substitution is accompanied by weaker LiO2 adsorption and lower calculated ORR/OER overpotentials. The LiO2 adsorption free energy emerges as a key activity descriptor, exhibiting correlations with the chalcogen p-band center, Mo d-band kurtosis, and Mo atomic charge. These findings provide a thermodynamic perspective on oxygen-induced surface reconstruction and its potential influence on the Li–O2 electrocatalytic properties of MoS2.