Lithium–sulfur (Li–S) batteries have been considered as promising energy storage systems due to the merits of high energy density and low cost. However, the lithium polysulfides (LiPSs) diffusion and sluggish redox kinetics hamper the battery performance. In this work, low-bandgap indium oxide (In₂O₃) with dense oxygen vacancies (In₂O_3−x, 0 < x < 3) confined in nitrogen-doped carbon column (NC) is developed as a desirable LiPSs immobilizer and promoter to address these intractable problems. The NC confined In₂O_3−x with rich O vacancies (In₂O_3−x@NC) lowers the bandgap of 1.78 eV, strengthens the chemical adsorbability to LiPSs, and catalyzes the bidirectional Li₂S redox. Attributed to the structural and chemical cooperativities, the obtained sulfur electrodes exhibit a stable cycling over 550 cycles at 1.0 C and splendid rate capability up to 4.0 C. More significantly, when the sulfur-loading reaches as high as 5.5 mg·cm⁻², the cathodes achieve an areal capacity of 5.12 mAh·cm⁻² at 0.1 C. The strategy of NC confined catalyst with rich defects engineering demonstrates great promise in the development of practical Li–S batteries.

Sulfurized polyacrylonitrile (SPAN) cathode exhibits improved cycling stability in carbonate electrolytes due to the existent of –S_x²⁻– (2 ≤ n ≤ 4) units. However, it is still challenging for SPAN to achieve higher sulfur content, superior conductivity, and faster polysulfide conversion kinetics in ether electrolytes. Herein, polyacrylonitrile (PAN), 2-morpholinothiobenzothiazole (MBS), and FeCl₃ coated reduced graphene oxide (rGO) were used to fabricate advanced sulfur cathode through electrospinning technology to address these problems. During PAN sulfuration reactions, the MBS with abundant unsaturated bonds served as the vulcanization accelerator to facilitate the formation of longer chain sulfur species (–S₃–/–S₄–) and increase the sulfur content in the SPAN electrode system. Meanwhile, Fe_1−xS is in situ converted from FeCl₃, which acts as the electrocatalyst to promote Li₂S nucleation and decomposition reactions. As a result, the Fe_1−xS/SPAN/rGO electrode with high sulfur loading of 2.0 mg·cm⁻² delivers a reversible capacity of 1122 mAh·g⁻¹ at 0.1 A·g⁻¹. Notably, at a large current density of 5.0 A·g⁻¹, the Fe_1−xS/SPAN/rGO electrode still displays a high specific capacity of 924 mAh·g⁻¹ with an ultra-stable cycling life over 2000 cycles. The present work provides new insights into designing of high-performance electrode materials for long-lasting Li-S batteries.

P2-type layered metal oxides have been considered as one of the promising cathode candidates for high-performance Na-ion batteries (SIBs). However, it is still challenging to balance the contradiction of high energy density and long cycle life due to the structural degradation and sluggish ion diffusion dynamics. Here, the hierarchical P2-Na_2/3Ni_1/3Mn_2/3O₂ hollow microspheres assembled by nanosheets are constructed via a self-template approach. The obtained nanosheets with more exposed electrochemical active planes serving as desodiation/sodiation reactors can provide substantial Na⁺ channels, shorten the diffusion pathways, and accommodate the volume changes during charge/discharge process. Benefiting from the facile Na⁺ diffusion paths and optimal architecture modulation, the cathode delivers a high initial Coulombic efficiency of 96.0% with a high energy density of 299.7 Wh·kg⁻¹. The highly reversible structural evolutions processes are verified by galvanostatic intermittent titration technique (GITT) and operando electrochemical impedance spectroscopy (EIS) measurement, which would significantly improve the cycle stability (83.3% capacity retention at 1.0 C over 500 loops). Furthermore, the full cell assembled by hard carbon presents a high reversible capacity of 71 mAh·g⁻¹ at 0.2 C and promising capacity retention (91.5% after 50 cycles). The designing concept of morphological configuration in this work paves an accessible route for building high-performance electrode materials.

Hydrogen generation from water splitting is of great prospect for the sustainable energy conversion. However, it is still challenging to explore stable and high-performance electrocatalysts toward hydrogen evolution reaction (HER) from saline water such as seawater due to the chloride corrosion. Herein, we developed a self-supported heterogeneous bimetallic phosphide (Ni₂P-FeP) array electrode that possesses excellent HER performance in alkaline saline water with an overpotential of 89 mV at 10 mA·cm⁻² and long-term stability over 90 h at 200 mA·cm⁻². The analysis showed that the heterostructure between the interfaces of Ni₂P-FeP plays a pivotal role in promoting the activity of catalyst. Moreover, the bimetallic phosphide nanoarrays can be employed as a shield for chlorine-corrosion resistance in the saline water, ensuring the long-term durability of hydrogen generation. When employed for alkaline saline water electrolysis, a current density of 100 mA·cm⁻² is achieved at cell voltage of 1.68 V. This work presents an effective approach for the fabrication of high-performance electrode for HER in alkaline saline environments.

Two-electron oxygen reduction reaction (ORR) catalysts are essential for the electrosynthesis of hydrogen peroxide (H₂O₂). MXenes, a rising family of two-dimensional (2D) transition metal carbides, have been extensively studied for energy storage and (photo)electrocatalysis due to their rich chemical compositions and tunable electronic structures. In this work, three representative MXenes of Ti₃C₂T_x, V₂CT_x, and Nb₂CT_x were selected for H₂O₂ electrosynthesis and we found that MXenes are inherent two-electron ORR catalysts with high H₂O₂ selectivity. In addition, this work critically evaluates their electrocatalytic activity and stability. Interestingly, Nb₂CT_x catalyst maintains better electrocatalytic activity and higher stability for a long time test, although the stability of Ti₃C₂T_x and V₂CT_x catalysts is poor owing to the metal dissolution property of Ti and V in alkaline media. Moreover, the assembled device based on Nb₂CT_x catalyst presents a high H₂O₂ production and a rapid organic dye decoloration ability.

Developing highly efficient non-Pt catalysts for fuel cells and metal-air batteries is highly desirable but still challenging due to the sluggish oxygen reduction reaction (ORR). Herein, a facile and efficient strategy is demonstrated to prepare N-doped carbon encapsulated ordered Pd-Fe intermetallic (O-Pd-Fe@NC/C) nanoparticles via a one-step thermal annealing method. The obtained O-Pd-Fe@NC/C nanoparticles show enhanced ORR activity, durability and anti-poisoning capacity in both acid and alkaline medium. When O-Pd-Fe@NC/C serving as cathode catalyst for Zn-air battery, it exhibits higher voltage platform and superior cycling performance with respect to the Zn-air battery based on the mixture of Pt/C and Ir/C catalysts. The enhanced electrocatalytic performance can be ascribed to the formation of face-centered tetragonal (fct) Pd-Fe nanoparticles, the protective action of the N-doped carbon layer and the interface confinement effect between them. The in situ formed N-doped carbon shell not only restrains the Pd-Fe ordered intermetallics from aggregating effectively during the thermal annealing process, but also provides a strong anchoring effect to avoid the detachment of Pd-Fe nanoparticles from the carbon support during the potential cycling. This facile carbon encapsulation strategy may also be extended to the preparation of a wide variety of N-doped carbon encapsulated intermetallic compounds for fuel cell application.