Recently, transition metal dichalcogenides (TMDs), represented by MoS₂, have been proven to be a fascinating new class of electrocatalysts in hydrogen evolution reaction (HER). The rich chemical activities, combined with several strategies to regulate its morphologies and electronic properties, make MoS₂ very attractive for understanding the fundamentals of electrocatalysis. In this review, recent developments in using MoS₂ as electrocatalysts for the HER with high activity are presented. The effects of edges on HER activities of MoS₂ are briefly discussed. Then we demonstrate strategies to further enhance the catalytic performance of MoS₂ by improving its conductivity or engineering its structure. Finally, the key challenges to the industrial application of MoS₂ in electrocatalytic hydrogen evolution are also pointed out.

Low-dimensional layered transition metal dichalcogenides (TMDs) have recently emerged as an important fundamental research material because of their unique structural, physical and chemical properties. These novel properties make these TMDs a suitable candidate in numerous potential applications. In this review, we briefly summarize the properties of low-dimensional TMDs, and then focus on the various methods used in their preparation. The use of TMDs in electronic devices, optoelectronic devices, electrocatalysts, biosystems, and hydrogen storage is also explored. The cutting-edge future development probabilities of these materials and numerous research challenges are also outlined in this review.

Recently, micron-sized LiMn_1−xFe_xPO₄cathode materials have attracted attention due to its better rate capability and higher tap density than the nano-sized ones. However, the influence of the particle size on the energy density of micron-sized LiMn_1−xFe_xPO₄is still unknown. In this paper, we report the optimal particle size of the micron-sized LiMn_0.8Fe_0.2PO₄with enhanced electrochemical performance as cathode material in lithium-ion batteries (LIBs). The LiMn_0.8Fe_0.2PO₄sample with the particle size of ∼9.39μm delivers the initial discharge capacity of 124 mAh g⁻¹at 0.2 C rate with high capacity retention of 94.35% after 100 cycles, which is higher than that with the particle sizes of ∼2.71μm, ∼3.74μm, ∼6.41μm or ∼16.31μm. This structure with the specific capacity of 122 mAh g⁻¹at 0.5 C rate and 106 mAh g⁻¹at 3 C rate also exhibits excellent rate performances. The improved electrochemical performances are mainly derived from its fast Li⁺diffusion, which causes the higher ionic conductivity. The LiMn_0.8Fe_0.2PO₄sample with the particle sizes of ∼9.39μm also shows the highest tap density (0.68 g cc⁻¹) among the as-prepared samples. This finding provides a new way to enhance the energy density of other cathode materials.

Recently, the earth abundant material MoS2 has attracted considerable attention in electrocatalytic hydrogen evolution reaction (HER) due to its chemical stability and high electrocatalytic efficiency. However, the aggregation formed in nanosized MoS2 reduces the exposure of active edge sites which hampers its electrocatalytic HER activity. In this paper, we demonstrate a facile hydrothermal synthesis of MoS2 nanosheet/MoS2 flake (MSN/MSF) homostructures by using MoS2 flakes as templates. The feature and chemical composition of the homostructures were investigated by scanning electron microscopy, transmission electron microscopy, Raman characterization and X-ray diffraction. The unique structure of MSN/MSF homostructures provides abundant active edge sites in the edge and basal plane of MoS2 flakes, resulting in an enhanced electrocatalytic HER activity (the overpotential at the current density of 10 mA/cm2 is 260 mV, and the Tafel slope is 82 mV/decade). It is expected to become a potential substitute for expensive noble metals.