Role of sulfur vacancies in MoS(2) monolayers in stabilizing Co atoms for efficient CO oxidation

By performing first-principles calculations, a MoS(2) monolayer with a Co atom doped at the sulfur defect (Co-(S)MoS(2)) was investigated as a single-atom catalyst (SAC) for CO oxidation. The Co atom is strongly constrained at the S-vacancy site of MoS(2) without forming clusters by showing a high diffusion energy barrier, ensuring good stability to catalyze CO oxidation. The CO and O(2) adsorption behavior on Co-(S)MoS(2) surface and four reaction pathways, namely, the Eley–Rideal (ER), Langmuir–Hinshelwood (LH), trimolecular Eley–Rideal (TER) as well as the New Eley–Rideal (NER) mechanisms are studied to understand the catalytic activity of Co-(S)MoS(2) for CO oxidation. The CO oxidation is more likely to proceed through the LH mechanism, and the energy barrier for the rate-limiting step is only 0.19 eV, smaller than that of noble metal-based SACs. Additionally, the NER mechanism is also favorable with a low energy barrier of 0.26 eV, indicating that the Co-(S)MoS(2) catalyst can effectively promote CO oxidation at low temperatures. Our investigation demonstrates that the S-vacancy of MoS(2) plays an important role in enhancing the stability and catalytic activity of Co atoms and Co-(S)MoS(2) is predicted to be a promising catalyst for CO oxidation.