Examination of Tunable Edge Sites and Catalyst Deactivation in the MoS₂-Catalyzed Methanation of Syngas

Abstract

A simple and effective strategy based on NH 4 + intercalation and thermal treatment was developed to tune the edge sites of MoS 2 . The catalysts were characterized by X-ray diffraction, thermogravimetric, transmission electron microscopyenergy-dispersive X-ray, scanning electron microscopy, Raman spectroscopy, Brunauer−Emmett−Teller, X-ray photoelectron spectra, in situ Fourier-transform infrared (FT-IR) spectroscopy of NO adsorption, and CHNS elemental analysis. The intercalation of NH 4 + into the interlayers of MoS 2 with thermal treatment served to reduce numbers of stacking layers and generate edge-rich MoS 2 with disordered structures. An increase of NH 4 + intercalation resulted in a greater exposure of MoS 2 edges, which enhanced the conversion rate of CO in the methanation reaction. The FT-IR study of NO adsorption demonstrated that edge sites contributed to the catalytic activity. A decrease of the activity in the long-term (100 h) stability evaluation can be attributed to the sintering of MoS 2 , the formation of MoO 2 with a loss of active MoS 2 components. This study established the intercalation of NH 4 + into the MoS 2 layers with subsequent heat treatment as an effective means to tune the edge sites and the catalytic activity.