Tuning the MoS₂ surfaces for the catalytic reactions of Li-O₂ batteries via N-doping and S-vacancy engineering

The implementation of heteroatom doping and defect engineering has enabled the design of various catalysts by modulating the electronic properties suitable for Li-O₂ batteries. In this work, we investigate the effects of nitrogen doping and sulfur vacancies on the electronic structure and catalytic behavior of the MoS₂ surfaces using first-principles calculations. The partial density of states analysis shows that nitrogen doping and sulfur vacancies introduce states near the Fermi level, transforming the semiconducting MoS₂ into a metallic conductor. Nitrogen doping creates N active sites that preferentially interact with lithium species, while sulfur vacancies expose the undercoordinated Mo sites that strongly interact with oxygen species. Adsorption energy, charge-transfer, and pCOHP analyses demonstrate that the exposed Mo site activates O₂ by transferring electrons into the antibonding π*2p orbitals, weakening the O-O bond and forming a Mo-O bond. However, the N active site exhibits moderate Li-N interaction and optimal adsorption strength, which are stronger than those for the S site but weaker than those for the Mo site. This highlights the importance of N-doping and S-vacancy engineering for controlling reaction pathways through the modulation of intermediate adsorption behavior. Furthermore, the presence of a sulfur vacancy modulates the electronic structure of the adjacent N sites by shifting the N p-band center away from the Fermi level, thereby optimizing the adsorption strength. Free energy analysis indicates that the N active sites reduce the overall overpotentials for both the ORR and OER processes. The present work demonstrates that defect and doping engineering offers an effective strategy to control adsorption behavior and reaction pathways for high-performance Li-O₂ cathode catalysts.