Transition metal dichalcogenides (TMDs) consist of dozens of ultrathin layered materials that have significantly different properties due to their varied phases, which determine the properties and application range of TMDs. Interestingly, a controllable phase transition in TMDs is achieved extensively with the use of several methods. Thus, phase control is a promising way to fully exploit the potential of TMDs. This review introduces the recent rapid development of the study of the TMD phase control, starting from the basic conception of the phase and phase transition in TMDs to the strategies for obtaining phase control. The different strategies are roughly classified into several types based on their characteristics: doping, synthesis method, strain, thermal method, and interlayer coupling. Finally, an evaluation on the prospect of the emergent strategies is provided.

For lithium−sulfur batteries (LSBs), the dissolution of lithium polysulfide and the consequent "shuttle effect" remain major obstacles for their practical applications. In this study, we designed a new cathode material comprising MoSe 2 / graphene to selectively adsorb polysulfides on the selenium edges and thus to mitigate their dissolution. More specifically, fewlayered MoSe 2 was first grown on nitrogen-doped reduced graphene oxide (N-rGO) using the chemical vapor deposition method and then infiltrated with sulfur as the cathode for LSBs. An initial capacity of 1028 mA h g −1 was achieved for S/ MoSe 2 /N-rGO at 0.2 C, higher than 981 and 405.1 mA h g −1 for pure graphene and sulfur, respectively, along with enhanced cycling durability and rate capability. Moreover, the density functional theory simulation, in addition to the experimental adsorption test, X-ray photoelectron spectroscopy analysis, and transmission electron microscopy technique, reveals the dual roles that MoSe 2 plays in improving the performance of LSBs by functioning as the binding sites for lithium polysulfides and as the platform that enables fast Li-ion diffusion by reducing its diffusion barrier. The reported finding suggests that the transitionmetal selenides could be an efficient alternative material as the cathode for LSBs.

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Singlet oxygen (1O2) has been widely produced utilizing nanostructure-based photocatalysts, purposed for photodynamic therapy (PDT), wastewater treatment, and photo-oxygenation reactions. A rational design of heterogeneous photocatalysts is important for a high 1O2 quantum yield under visible-light or near-infrared irradiation. The present review provides insights for graphene-based photocatalyst design by summarizing the mechanism and fundamental aspects of 1O2 sensitization, as well as offers a summary of experimental realization. Subsequently, we go through works done on light-driven 1O2 sensitization utilizing graphitic carbon nitride, carbon dots, graphene quantum dots, and graphene oxide, as well as immobilized organic dyes on polymeric and silica supports, followed by their applications. Moreover, the effect of surface passivation, hybridization with other materials, doping with metal or nonmetal atoms, plasmonic fields, and self-assembly aggregation on the 1O2 quantum yield and 1O2 enhancement factor is discussed. We also provide perspectives for the 1O2 sensitization including applying machine learning (ML) to optimize the plasmonic field and 1O2 quantum yield.