Role of sulfur vacancies in MoS2 monolayers in stabilizing Co atoms for efficient CO oxidation

By performing first-principles calculations, a MoS2 monolayer with a Co atom doped at the sulfur defect (Co-(MoS2)-Mo-S) was investigated as a single-atom catalyst (SAC) for CO oxidation. The Co atom is strongly constrained at the S-vacancy site of MoS2 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-(MoS2)-Mo-S 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-(MoS2)-Mo-S 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-(MoS2)-Mo-S catalyst can effectively promote CO oxidation at low temperatures. Our investigation demonstrates that the S-vacancy of MoS2 plays an important role in enhancing the stability and catalytic activity of Co atoms and Co-(MoS2)-Mo-S is predicted to be a promising catalyst for CO oxidation.