Lithium-sulfur (Li-S) batteries, known for their high energy density, are attracting extensive research interest as a promising next-generation energy storage technology. However, their widespread use has been hampered by certain issues, including the dissolution and migration of polysulfides, along with sluggish redox kinetics. Metal sulfides present a promising solution to these obstacles regarding their high electrical conductivity, strong chemical adsorption with polysulfides, and remarkable electrocatalytic capabilities for polysulfide conversion. In this review, the recent progress on the utilization of metal sulfide for suppressing polysulfide shuttling in Li-S batteries is systematically summarized, with a special focus on sulfur hosts and functional separators. The critical roles of metal sulfides in realizing high-performing Li-S batteries have been comprehensively discussed by correlating the materials’ structure and electrochemical performances. Moreover, the remaining issues/challenges and future perspectives are highlighted. By offering a detailed understanding of the crucial roles of metal sulfides, this review dedicates to contributing valuable knowledge for the pursuit of high-efficiency Li-S batteries based on metal sulfides.

Metal-free catalyst for photocatalytic production of H₂O₂ is highly desirable with the long-term vision of artificial photosynthesis of solar fuel. In particular, the specific chemical bonds for selective H₂O₂ photosynthesis via 2e^– oxygen reduction reactions (ORR) remain to be explored for understanding the forming mechanism of active sites. Herein, we report a facile doping method to introduce boron-nitrogen (B–N) bonds into the structure of graphitic carbon nitride (g-C₃N₄) nanosheets (denoted as BCNNS) to provide significant photocatalytic activity, selectivity and stability. The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer. The units are also proved to be superior active sites for selective O₂ adsorption and activation, reducing the energy barrier for *OOH formation, and thereby enabling an efficient 2e^– ORR pathway to H₂O₂. Consequently, with only bare loss of activity during repeated cycles, the optimal H₂O₂ production rate by BCNNS photocatalysts reaches 1.16 mmol·L^–1·h^–1 under 365 nm-monochrome light emitting diode (LED_365nm) irradiation, increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts. This work gives the first example of applying B–N bonds to enhance the photocatalytic H₂O₂ production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.

Due to their superior hydrophilicity and conductivity, ultra-high volumetric capacitance, and rich surface-chemistry properties, MXenes exhibit unique and excellent performance in catalysis, energy storage, electromagnetic shielding, and life sciences. Since they are derived from ceramics (MAX phase) through etching, one of the challenges in MXenes preparation is the inevitable exposure of metal atoms on their surface and embedding of anions and cations. Because the as-obtained MXenes are always in a thermodynamically metastable state, they tend to react with trace oxygen or oxygen-containing groups to form metal oxides or degrade, leading to sharply declined activity and impaired performance. Therefore, improving the stability of MXenes-based materials is of practical significance in relevant applications. Unfortunately, there lacks a comprehensive review in the literature on relevant topics. To help promote the wide applications of MXenes, we review from the following aspects: (i) insights into the factors affecting the stability of MXenes-based materials, including oxidation of MXenes flakes, stability of MXenes colloidal solutions, and swelling and degradation of MXenes thin-film, (ii) strategies for enhancing the stability of MXenes-based materials by optimizing MAX phase synthesis and modifying the MXenes preparation, and (iii) techniques for further increasing the stability of freshly prepared MXenes-based materials via controlling the storage conditions, and forming shielding on the surface and/or edge of MXenes flakes. Finally, some outlooks are proposed on the future developments and challenges of highly active and stable MXenes. We aim to provide guidance for the design, preparation, and applications of MXenes-based materials with excellent stability and activity.

Transition metal phosphides (TMPs) are promising candidates for sodium ion battery anode materials because of their high theoretical capacity and earth abundance. Similar to many other P-based conversion type electrodes, TMPs suffer from large volumetric expansion upon cycling and thus quick performance fading. Moreover, TMPs are easily oxidized in air, resulting in a surface phosphate layer that not only decreases the electric conductivity but also hinders the Na ion transport. In this work, we present a general electrode design that overcomes these two major challenges facing TMPs. Using metal hydroxide and glucose as precursors, we show that the metal hydroxide can be converted into phosphide whereas the glucose simultaneously decomposes and forms carbon shell on the phosphide particles under a plasma ambient. Ni₂P@C core shell structures as a proof-of-concept are designed and synthesized. The in situ formed carbon shell protects the Ni₂P from oxidation. Moreover, the high-energy plasma introduces porosity and vacancies to the Ni₂P and more importantly produces phosphorus-rich nickel phosphides (NiP_x). As a result, the Ni₂P@C electrodes achieve high sodium capacity (693 mAh·g⁻¹ after 50 cycles at 100 mA·g⁻¹) and excellent cyclability (steady capacity maintained for at least 1, 500 cycles). Our work provides a general strategy for enhancing the sodium storage performance of TMPs, and in general many other conversion type electrode materials that are unstable in air and suffer from large volumetric changes upon cycling.