Abstract
The treatment of hazardous hydrogen sulfide (H2S) via photocatalysis technology has been known as one of the most promising green technologies. Photocatalytic production of hydrogen (H2) from H2S by two-dimensional (2D) semiconductor materials has gathered great attention owing to its large surface area and high catalytic activity. In this work, layered MoS2 has been successfully grown on TiO2 {001} surface to fabricate the 2D MoS2/TiO2 {001} composites for H2 evolution from H2S, which can be confirmed by the X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests. Band structures and UV-Vis spectra provide important evidences that MoS2 loading can significantly narrow the band gap and broaden the light absorbance into the visible light region. Electron transfer is obviously visualized at the interface of MoS2/TiO2, resulting in the built-in potential from TiO2 to MoS2, which is determined by the density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) test. Consequently, the photo-induced electrons and holes are accumulated at the sides of TiO2 and MoS2 under the illumination, respectively, which largely promote the interfacial electron transfer and prolong the lifetime of photo-generated electrons that participate in the photocatalytic reactions of H2 evolution from H2S. This efficient separation of photo-induced carriers can be further proved by photoluminescence (PL) spectra, photocurrent responses, and electrochemical impedance spectra. As a result, the photocatalytic activity of H2 evolution is largely increased by 9.4 times compared to the pristine TiO2. This study could offer a new and facile way to design highly efficient 2D photocatalysts for the application of H2S treatment.
Highlights
Hydrogen sulfide (H2S), as a highly toxic and corrosive pollutant, has been massively discharged from the natural gas extraction and oil refineries, which causes a serious threat on the air environment and human health with a fatal concentration over 700 ppm in the air
Other researchers found that the MoS2 nanosheets grown on TiO2 could produce more active edges, and the efficient separation of the photo-generated carries resulted in the excellent H2 production from H2O (Liu Q. et al, 2013; Zhang et al, 2015)
PL intensity and higher photocurrent response of MoS2/TiO2 caused by the interfacial electron transfer mechanism reveals the high efficiency of photo-generated carrier separation, which can be the key factor for high H2 evolution
Summary
Hydrogen sulfide (H2S), as a highly toxic and corrosive pollutant, has been massively discharged from the natural gas extraction and oil refineries, which causes a serious threat on the air environment and human health with a fatal concentration over 700 ppm in the air. The high cost and limited storage of noble metals are of serious concerns It deserves to develop economy and efficient methods to modify TiO2 to achieve a high conversion activity of H2. Various researches have reported that the layered MoS2 can act as an excellent cocatalyst for both photocatalytic and electrocatalytic evolution of H2 owing to the abundantly exposed edges (Li et al, 2011; Kibsgaard et al, 2012; Chang et al, 2014). Other researchers found that the MoS2 nanosheets grown on TiO2 could produce more active edges, and the efficient separation of the photo-generated carries resulted in the excellent H2 production from H2O (Liu Q. et al, 2013; Zhang et al, 2015). The promising MoS2/TiO2 composite has been barely applied to H2 evolution from H2S as yet, and the enhanced photocatalytic mechanism of H2 production deserves in-depth study. The morphology, component, optical properties, and interfacial electron transfer of the fabricated MoS2/TiO2 {001} are investigated in-depth by experimental tests such as transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra as well as the density functional theory (DFT) calculations
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