Ex Situ Characterization of 1T/2H MoS₂ and Their Carbon Composites for Energy Applications, a Review

Abstract

The growing interest in the development of next-generation net zero energy systems has led to the expansion of molybdenum disulfide (MoS 2 ) research in this area. This activity has resulted in a wide range of manufacturing/synthesis methods, controllable morphologies, diverse carbonaceous composite structures, a multitude of applicable characterization techniques, and multiple energy applications for MoS 2 . To assess the literature trends, 37,347 MoS 2 research articles from Web of Science were text scanned to classify articles according to energy application research and characterization techniques employed. Within the review, characterization techniques are grouped under the following categories: morphology, crystal structure, composition, and chemistry. The most common characterization techniques identified through text scanning are recommended as the base fingerprint for MoS 2 samples. These include: scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Similarly, XPS and Raman spectroscopy are suggested for 2H or 1T MoS 2 phase confirmation. We provide guidance on the collection and presentation of MoS 2 characterization data. This includes how to effectively combine multiple characterization techniques, considering the sample area probed by each technique and their statistical significance, and the benefit of using reference samples. For ease of access for future experimental comparison, key numeric MoS 2 characterization values are tabulated and major literature discrepancies or currently debated characterization disputes are highlighted.

Single-Atom Platinum Anchored on Submonolayer MoS2–x for Efficient Hydrogen Evolution

“…Notably, the Tafel slope of the Pt-SM-MoS 2– x sample is lower than 120 mV/dec, which means that the sluggish Volmer reaction previously observed for SM-MoS 2– x is significantly accelerated . The appreciably different catalytic HER properties of Pt-2D-MoS 2 and Pt-SM-MoS 2– x demonstrate that the common SM-MoS 2– x substrate can significantly benefit HER catalysis as Pt-SM-MoS 2– x , which is ascribable to strong H adsorption promoted by the assisting sites in SM-MoS 2– x , including exposed Mo atoms, with their negative hydrogen adsorption energies, that are located near the loaded Pt atoms.…”

“…How the 2D-MoS 2 and SM-MoS 2– x substrates influence the single-atom Pt catalysts was next investigated by examining the electrocatalytic HER performance of 2D-MoS 2 , Pt-2D-MoS 2 , SM-MoS 2– x , and Pt-SM-MoS 2– x . The linear sweep voltammetry (LSV) curves in Figure a show that the examined Pt-SM-MoS 2– x sample delivers an overpotential of 144 mV at 10 mA/cm 2 , while higher overpotentials of 523, 269, and 308 mV are needed for 2D-MoS 2 , Pt-2D-MoS 2 , and SM-MoS 2– x , respectively (Figure S5), highlighting that Pt-SM-MoS 2– x exhibits superior HER activity . The lower activity of Pt-2D-MoS 2 suggests that the inert basal plane of 2D-MoS 2 limits the loading of Pt atoms on the surface compared to the SM-MoS 2– x substrate.…”

“…Efficient catalysts for the hydrogen evolution reaction (HER) play key roles in realizing the hydrogen economy and a future green and sustainable society. − In particular, single-atom catalysts (SACs) with high mass catalytic activity can largely reduce the consumption of noble metals, such as scarce Pt, Ru, etc., which are ideal candidates for HER catalysts but are limited by their scarcity. − Therefore, noble metal-based SACs are considered to be promising HER electrocatalysts. − Great efforts have been made to develop SACs to accelerate the chemical reaction rate of various chemical reactions . Recent SAC advances have shown that well-constructed substrates not only stabilize metal atoms through strong coordination but also provide assisting sites that further improve overall catalytic activity. − However, realizing SACs that behave in such a synergistic catalytic paradigm using conventional supports, such as carbon-based materials, , metal oxides, , carbides, nitrides, etc., remains greatly challenging due to weak substrate–metal interaction (SMI) or low conductivity.…”

Are sodiation/de-sodiation reactions reversible in two-dimensional metallic NbSe2?

“…This is distinct from the most reported TMD materials that performed reversible conversion reactions for alkali metal ion storage. 3,18–21…”

“…A recent work reported that NbSe 2 electrodes underwent sequential reversible sodiation steps of intercalation and conversion reactions, 17 which was analogous to many other TMD anodes for alkali metal ion storage. 3,18–21 Differently, D. W. Kim et al believed that only intercalation and de-intercalation reactions occurred in NbSe 2 anodes without any conversion reactions in its crystal structure upon sodiation/de-sodiation. 22 Generally, the question of whether NbSe 2 or other metallic TMD anodes for Na ion storage really perform reversible or irreversible reactions is still under considerable debate.…”