Electron-Doped 1T-MoS2 via Interface Engineering for Enhanced Electrocatalytic Hydrogen Evolution

Designing advanced electrocatalysts for hydrogen evolution reaction is of far-reaching significance. Active sites and conductivity play vital roles in such a process. Herein, we demonstrate a heteronanostructure for hydrogen evolution reaction, which consists of metallic 1T-MoS2 nanopatches grown on the surface of flexible single-walled carbon nanotube (1T-MoS2/SWNT) films. The simulated deformation charge density of the interface shows that 0.924 electron can be transferred from SWNT to 1T-MoS2, which weakens the absorption energy of H atom on electron-doped 1T-MoS2, resulting in superior electrocatalytic performance. The electron doping effect via interface engineering renders this heteronanostructure material outstanding hydrogen evolution reaction (HER) activity with initial overpotential as small as approximately 40 mV, a low Tafel slope of 36 mV/dec, 108 mV for 10 mA/cm, and excellent stability. We propose that such interface engineering could be widely used to develop new catalysts for energy conversion application. B of its high energy density and environment-friendly impact, hydrogen is advocated as an alternative energy carrier in the future. Sustainable and efficient production of hydrogen is a prerequisite for realization of the hydrogen economy. Therefore, considerable efforts have been devoted to designing HER electrocatalysts possessing a small overpotential and low Tafel slope. As the most active and chemically stable electrocatalyst for HER, platinum (Pt) suffers from high cost in terms of upscaling; yet it is challenging to find an alternative electrocatalyst to replace Pt. Fortunately, the exploitation of MoS2 compounds as potential robust and efficient catalysts for HER has opened a promising new path for this field. Both theoretical and experimental research has proved that increasing the number of metallic Mo edge sites (unsaturated sulfur atoms) is a crucial factor to enhance HER activity. Great efforts have been made concentrating on improving the number of active edge sites through nanostructuring such as a molecular MoS2 edge site mimic, amorphous molybdenum sulfides, highly ordered double-gyroid MoS2 bicontinuous network, MoS2 films with vertically aligned layers, defect-rich MoS2 ultrathin nanosheets, MoS2 nanosheet with strained sulfur vacancies in its basal planes, and so on. Metallic 1T-MoS2, different from the above semiconducting 2H-MoS2, possesses Mo−S octahedral coordination, through rotating one of the S−Mo−S basal planes by 60° around the caxis from the trigonal prism 2H structure. Much research has demonstrated that charge transfer kinetics in metallic 1T-MoS2 is also a key parameter to further improve HER performance. Theoretical calculations show that such 2H-1T phase engineering endows the inert basal plane activation a lowering of ΔGH at +0.18 eV for 1T from +1.6 eV for 2H, equal to 2H-MoS2 edges on Au(111), known as one of the most active catalysts for hydrogen evolution. Similar enhancements in the HER kinetics through intergrating 2H-MoS2 nanostructures with a variety of conducting supports such as reduced graphene oxide, carbon nanotubes, carbon cloths, and carbon fibers have also been observed. Besides maximizing the active sites at both edge and basal plane, phase engineering, and intergrated 2H phase with conducting substrate, how to further activate and optimize the MoS2 for hydrogen evolution is still highly desirable. Given the typical ultrathin 2D geometric features of MoS2, the electronic perturbations derived from the Received: February 3, 2017 Revised: May 8, 2017 Published: May 8, 2017 Article