摘要 : Nickel selenide, as hybrid supercapacitor electrode material, has excellent electrochemical performance. However, it also faces challenges, such as slow charge transfer speed, easy agglomeration, and volume expansion. Here, we prepared a high crystalline graphitic carbon nitride (CCN)/biochar (C)/nickel selenide (NiSe 2 ) (CCN/C-NiSe 2 ) ternary composite material as the positive electrode to solve the problems mentioned above. After introduction of C, the few layers and low body phase of g-C 3 N 4 (CN) can be obtained by utilizing its self-assembly and micro-reaction space characteristics. Furthermore, CN with many defects and low crystallinity degree can be improved by introducing molten salt system, so as to obtain CCN. The strong interconnections between the π-conjugated layer of CCN and the biochar promote electron and ion transport efficiency, which can increase the charge transfer speed, decrease accumulation agglomeration and poor stability of NiSe 2 . The results show that the specific capacitance of CCN/C-NiSe 2 -90 nanocomposite electrode is 1309.75 F g −1 (1 A g −1 ), which is significantly higher than that of NiSe 2 (965.75 F g −1 ) and CCN/C (74 F g −1 ) in the three-electrode system. The CCN/C-NiSe 2 -90//AC presents energy density of 28.66 Wh kg −1 at 849.88W kg −1, and its initial performance maintains 80 % capacitance after 5000 cycles (5 A g −1 ).

摘要 : Regulation of the second nearest neighbor coordination atoms is a potent strategy for enhancing electrocatalytic oxygen reduction reaction (ORR) activity of manganese-nitrogen-carbon (Mn–N–C) catalysts with Mn–N 4 sites. However, precisely regulating the second-nearest neighbor coordination environment of the Mn site is still challenging. Here, a novel approach is proposed to modulate the local microenvironment of Mn–N 4 sites by strategically doping sulfur (S) atoms at the second nearest neighbor coordination positions to address this challenge. Density functional theory calculations elucidate that S-doping at these positions significantly alters the charge distribution of the Mn site, inducing a downshift in the d -band center of Mn. This electronic modulation weakens the binding strength of the Mn site toward the OH intermediate, thereby reducing the energy barrier for the ORR process. To experimentally realize this concept, the strategic molecular assembly approach is employed to precisely incorporate S atoms into the second nearest neighbor coordination of the Mn site, resulting in the construction of the manganese-nitrogen-sulfur-carbon (Mn–N–S–C) catalysts. The Mn–N–S–C showcases a favorable half-wave potential of 0.913 V. When integrated into rechargeable liquid zinc-air batteries (ZABs) the Mn–N–S–C-based ZABs deliver high power density of 209.8 mW cm −2 and stable cycling performance for 800 h. Furthermore, Mn–N–S–C-based quasi-solid-state ZABs exhibit a power density of 34.05 mW cm −2 and a cycle life of 23 h. This study highlights the importance of the second nearest neighbor coordination atoms in tuning the electronic structure of single atom active sites, proposes a method to enhance ORR efficiency through atomic-level engineering, and demonstrates the practical application of the Mn–N–S–C catalyst in high-performance energy storage systems. These findings provide valuable insights into the design principles for next-generation catalyst design and support advancements in energy conversion and storage technologies.

摘要 : Molybdenum-based materials, such as MoO 2 and MoS 2, have gathered significant attention in lithium-ion battery research because of their high theoretical specific capacity. However, their practical use is constrained by inherent low conductivity and structural degradation that occurs in the lithiation/delithiation processes. Herein, uniform core-shell C-MoO 2 @C-MoS 2 microspheres with a diameter of ca. 1.2 μm were successfully fabricated through synchronous reduction and sulfidation of MoO 3, using an economical glucose as carbon resource, co-reductant, and structure directing agents. In-situ XRD analysis reveals the excellent reversibility and structural stability of C-MoO 2 @C-MoS 2 during the charge-discharge cycle. Moreover, the unique core-shell structure also endows C-MoO 2 @C-MoS 2 with a high reversible lithium storage capacity (377 mAh·g −1 after 550 cycles at 0.1 A g −1, coulombic efficiency >99.5 %), low charge-transfer resistance (52.4 Ω), and a high Li + diffusion kinetics ( D Li+ = 3.89 × 10 −11 cm 2 s −1 ). Notably, C-MoO 2 @C-MoS 2 contributes significantly to the interlayer capacitance, accounting for 69 % at 1.0 mV s −1 . This study offers a novel and straightforward approach for constructing core-shell structured composites with potential applications in new energy technologies.

摘要 : A copper nanoparticles@porous biocarbon substrate was designed for Surface-Enhanced Raman Spectroscopy (SERS) via a simple reduction method. In the detection of three trace antibiotics, the substrate exhibits a very high Raman enhancement efficiency. This is partly because the biocarbon is rich in meso-micropores, which can rapidly trap target molecules. On the other hand, the copper nanoparticles embedded on the surface of the carbon sheets generate a large number of plasmonic hotspots, leading to an increase in Raman signal intensity. These results suggest that this substrate has utility for SERS applications in food safety, medicine, and water pollution detection.

摘要 : The introduction of nitrogen defects in graphitic carbon nitride (g-C3N4) has the important effect of improving its photocatalytic performance. This study employs a simple and environmentally friendly one-step pyrolysis method, successfully preparing g-C3N4 materials with adjustable N3C defect concentrations through the calcination of a urea and ammonium acetate mixture. By introducing N3C defects and adjusting the band structure, the conduction band of the g-C3N4 was shifted downward by 0.12 V, overcoming the traditional application limitations of N3C defects and enabling an innovative transition from enhanced oxidation to enhanced reduction capabilities. This transition significantly enhanced the adsorption and activation of O2. Characterization results showed that the introduction of N3C defects increased the specific surface area from 44.07 m2/g to 87.08 m2/g, enriching reactive sites, while narrowing the bandgap to 2.41 eV enhanced visible light absorption capacity. The g-C3N4 with N3C defects showed significantly enhanced photocatalytic activity, achieving peak performance of 54.8% for tetracycline (TC), approximately 1.5 times that of the original g-C3N4, with only a 5.4% (49.4%) decrease in photocatalytic efficiency after four cycles of testing. This study demonstrates that the introduction of N3C defects significantly enhances the photocatalytic performance of g-C3N4, expanding its potential applications in environmental remediation.

摘要 : Atomically dispersed tungsten-nitrogen-carbon with W−N 4 sites acts as a highly efficient catalyst for oxygen reactions. However, the symmetrical charge distribution of W−N 4 sites results in strong binding with oxygen-containing intermediates, leading to unsatisfactory catalytic activities. Here, an axially coordinated sulfur (S) atom is integrated into the atomically dispersed W−N 4 site and anchored onto multi-walled carbon nanotubes (S 1 −W 1 N 4 −MWCNTs) for oxygen reduction/oxygen evolution reactions (ORR/OER). The axial S atom, with significantly different electronegativity and outer electronic structure compared to nitrogen atom, induces localized charge redistribution around W−N 4 site. This change optimizes the adsorption/desorption capabilities of oxygen-containing intermediates on W−N 4 site, thereby enhancing the overall oxygen reaction activities. The S 1 −W 1 N 4 −MWCNTs demonstrates excellent ORR/OER activity with the half-wave potential of 0.916 V for ORR and the potential of 1.644 V (at 10 mA cm −2 ) for OER. At −20 °C, S 1 −W 1 N 4 −MWCNTs-based zinc-air batteries demonstrate increased specific capacity and an extended charging-discharging cycle life of 420 h, surpassing performance at room temperature. Regulating the charge distribution of W−N 4 sites with axial S atoms provides an effective strategy to boost the oxygen reaction activities of tungsten-nitrogen-carbon catalysts.

摘要 : A high nickel content layered cathode material such as LiNi0.92Co0.04Mn0.04O2 (N92) is regarded as an extremely promising candidate for a next-generation high-energy-density lithium ion battery (LIB) owing to the large specific capacity and low cost. Nonetheless, some undesirable defects, including structure instability, large cation mixing between Ni2+ and Li+, and serious side reactions caused by high oxidation of Ni4+, have made this competitor difficult to put into a practical application. In the present work, the high speed mill-balling method is adopted to prompt the lithium superionic conductor Li0.388Ta0.238La0.475Cl3 (LTLC) cover on the surface of N92 particles to enhance the large rate and low-temperature discharge performance, maintain the cyclic stability, and strengthen the safety behaviors. As a result, the LTLC covering layer accompanied by La3+ and Ta5+ doping could not only suppress the side reactions and enhance the whole structure stability of a cathode but also contribute to improving the Li+ intercalation/deintercalation efficiency from the cathode material interface and accelerating the Li+ diffusion rate in the cathode bulk. Compared to N92, the cathode after 2% LTLC covering indeed demonstrates much better electrochemical properties and enhanced safety performance, which exhibits great practicality when applied in high-energy-density LIB.

摘要 : Tetracyclines (TCs), a class of broad-spectrum antibiotics, are major contaminants in water, have adverse effects on the ecosystem, and are toxic non-target organisms. A straightforward and efficient strategy for both the detection and removal of TCs from water remains highly desirable but is challenging to develop. In this study, a dual-functional platform for detecting and removing TCs was developed using highly stable silver-based metal-organic frameworks (Ag-MOFs). This platform enabled the specific detection of TCs over a broad concentration range (from 1 × 10⁻10 to 1 × 10⁻3 mol/L), with a low detection limit of 8.4 nM. By leveraging its high surface area, the Ag-MOFs exhibited exceptional adsorption capacities, reaching 276 mg/g for chlortetracycline. To elucidate the potential response mechanism and electronic transfer pathway, density functional theory calculations and charge density difference analyses were performed. This Ag-MOFs-based platform achieved both rapid detection and efficient removal of TCs from the environment. The design principles proposed herein are expected to inspire the development of novel platforms for the simultaneous sensing and removal of specific pollutants.

摘要 : Nickel hydroxide (Ni(OH)2) is recognized as a promising material for electrodes in supercapacitors owing to its exceptional theoretical specific capacitance. However, Ni(OH)2 has several drawbacks, including a short cycle life, susceptibility to volume expansion, and poor electrical conductivity. In this work, Ni(OH)2 nanosheets anchored on layered g-C3N4/C (Ni(OH)2–g–C3N4/C) are designed by biological template induction and a hydrothermal method. Ni(OH)2–g–C3N4/C has unique petal-like structures, which can provide a vertical charge transport channel to increase reaction potential of the material during the charge–discharge process. The introduction of biomass carbon can solve the problem of the bulk phase accumulation of g-C3N4 and can also improve the overall conductivity of the composite. Compared to Ni(OH)2 (522 F g−1), g-C3N4/C (76.2 F g−1), and g-C3N4 (16 F g−1), the Ni(OH)2–g–C3N4/C-0.75 (NGC-0.75) composite exhibits the highest specific capacitance of 1034 F g−1 at 1 A g−1. Furthermore, after 5000 cycles at 5 A g−1, the capacitance of the material is maintained at 85.97%. Meanwhile, the asymmetric supercapacitor based on the NGC-0.75 shows a high energy density of 18.29 Wh kg−1 at the power density of 400.02 W kg−1 with excellent cyclic stability of 127.45% over 10 000 cycles.

摘要 : Graphite phase carbon nitride (g-C3N4), a polymer semiconductor with a typical two-dimensional layered structure and narrow band gap, has excellent visible light absorption capacity, stable physical and chemical properties and good photocatalytic properties. However, the structure of g-C3N4 produced by the heat-induced polymerization from traditional nitrogen-containing precursor is incomplete. The main body is melon-based carbon nitride with amorphous or semi-crystalline structure. There are many defects in its phase and surface, which lead to lower conductivity, higher electron-hole pairs recombination rate, resulting in lower catalytic activity. Therefore, it is necessary to improve the crystallinity of g-C3N4. This paper mainly summarizes the advantages of high crystalline carbon nitride (CCN) and the research progress in recent years. Increasing the crystallinity of g-C3N4 can provide charge transfer channels between the conjugated planes to improve the charge transfer efficiency, and also introduce other modification methods to achieve efficient synergies. Then, the structure, characterization, preparation, modification strategy and application fields of CCN in recent years were reviewed. Finally, the challenges and future development directions of CCN photocatalysts are summarized briefly.