Engineering unsaturated sulfur site in three-dimension MoS2@rGO nanohybrids with expanded interlayer spacing and disordered structure for gaseous elemental mercury trap

Rapid and effective capture of gaseous elemental mercury (Hg0) over a wide operating temperature range is significant for the green and sustainable development of nonferrous smelting industry. High mercury affinity and strong sulfur resistance of two-dimensional layered MoS2 render it an outstanding adsorbent for Hg0 trap. However, the relative lack of serviceable active sites greatly suppresses its extensive application. Herein, a feasible strategy to expand interlayer spacing, build disordered structure and engineer unsaturated sulfur adsorption sites was provided through the construction of three-dimension MoS2@rGO nanohybrids. As ex-pected, compared with bulk and ordered MoS2, the prepared MoS2@rGO hybrid exhibits a remarkable perfor-mance improvement for Hg0 adsorption. The average Hg0 adsorption rate of MoS2@rGO is 2.28 mu g/g/min and its saturated adsorption capacity reaches 20.91 mg/g. The typical components in nonferrous flue gas have almost no effect on Hg0 adsorption performance. X-ray photoelectron spectroscopy confirms that the formation of abundant unsaturated coordination sulfurs sites with high thermostability is critical for Hg0 adsorption performance improvement. Moreover, the density functional theory calculation results further demonstrate the high adsorption activity of unsaturated coordination sulfur sites for Hg0 capture. Among these sulfur sites, edge sulfur vacancy site plays a dominant role for Hg0 adsorption because of the lowest Hg0 adsorption energy. The final adsorption production is HgS which has negligible environmental toxicity due to its extreme stability. This work not only provides a promising adsorbent for Hg0 removal in industrial application, but also opens up an avenue to engineer unsaturated sulfur for other layered transition metal dichalcogenides.

Automated summary

By constructing three-dimensional MoS2@rGO nanohybrids, interlayer spacing can be expanded, disordered structure can be built, and unsaturated sulfur adsorption sites can be engineered, resulting in a remarkable improvement in adsorption performance for Hg0.