Activation of the MoS 2 Basal Plane to Enhance CO Hydrogenation to Methane Activity Through Increasing S Vacancies.

The active site of MoS 2 is usually located at the edge of crystalline MoS 2 , which has a lower proportion than that from the basal plane, limiting the hydrogenation activity. Therefore, activating the basal plane of MoS 2 is expected to greatly enhance the hydrogenation activity. Herein, we prepared a series of MoS 2 catalysts by acidolysis of ammonium tetrathiomolybdate and subsequently pyrolyzing at high temperature with different atmospheres. Through analysis, we found that the prepared MoS 2 catalysts were curved, which was different from commercial MoS 2 . Through X-ray diffraction, transmission electron microscopy, and Raman and X-ray photoelectron spectroscopy characterization, it was found that the MoS 2 catalyst pyrolyzed under a N 2 atmosphere had a larger number of S-vacancies than the MoS 2 catalysts under a H 2 atmosphere. In addition, temperature-programmed reduction results showed that the Mo-S bond energy was decreased with the increasing content of S-vacancies, which might be related to bending. Sulfur-resistant methanation results indicated that the curved MoS 2 exhibited increased CO conversion with the increasing S vacancies. Furthermore, density functional theory calculation was used to simulate the generation of S vacancy and numbers of S vacancies. It was found that with the generation of S vacancy, three unsaturated coordination Mo atoms were exposed around one S vacancy and became new active sites, resulting in enhanced activity. What is more, the higher methanation activity was attributed not only from more S vacancies but also from the decreased activation energy for CO hydrogenation activation.