Search

Molybdenum disulfide (MoS2) has significant potential in aqueous zinc-ion batteries (AZIBs) due to its unique layered structure and adjustable layer spacing. However, the electrochemical performance remains unsatisfactory primarily due to the limited interlayer spacing. Here, a composite material consisting of MoS2 nanosheets with expanded interlayer spacing and intercalated surfactant polyethylene glycol (PEG) is proposed as a cathode material for AZIBs. The results indicate that PEG is intercalated into the layered structure of MoS2, resulting in a significant expansion of the MoS2 layer spacing (from 0.62 to 0.95 nm). The PEG effectively mitigates the agglomeration during MoS2 growth, promotes the 2H to 1T phase conversion in MoS2 (about 60% of 1T phase content), provides more active sites for electrochemical reactions, reduces electron transfer resistance, and shortens diffusion distance of zinc ions. During the process of charging and discharging, the intercalated PEG molecules serve as "pillars" to provide structural support for MoS2 layers, thereby enhancing their stability. The pseudocapacitive behavior of the MoS2-PEG is promoted by the combination of these aforementioned advantages. Consequently, the MoS2-PEG composite electrode exhibited a discharge capacity of 123.4 mAh·g−1 at a current density of 1.0 A g−1 and maintained a capacity retention of 83.5% after 200 cycles, while pure MoS2 only displayed a reversible capacity of 71.5 mAh·g−1 under identical conditions. This study provides a reference for the development of MoS2 as a cathode material for AZIBs. [ABSTRACT FROM AUTHOR]

Pesticide residues are a serious problem towards agriculture, environment and food safety, so it is highly desirable to develop a swift, efficient and portable pesticide detection method. A fluorescence visual sensing method for glyphosine based on a nitrogen-doped biomass carbon quantum dot (N-CQD) paper-based sensor was developed. The fluorescence signal was quenched by Fe3+ in a static quenching process, and then the fluorescence of N-CQDs was recovered after adding glyphosine. Under the optimal experimental conditions and when tested with a fluorescence spectrofluorometer, the detection of glyphosine showed a two-stage linear pattern in the range of 0.1–0.6 μM and 0.6–1.6 μM with a detection limit of 0.075 μM. Then, the RGB values of different concentrations of glyphosine on the filter paper chip were detected by the software of the smartphone-color identifier. The logarithm of the glyphosine concentration was linearly related to the G value of RGB in the range of 0.25–10.00 mM and with a detection limit of 0.15 mM. The method was applied to measuring glyphosine-spiked juice and flour samples, and the recovery rates were 87.60–112.69% and 93.27–105.83%, respectively. The proposed N-CQDs/Fe3+ system had wide applications, and it was expected to be fast and effective at detecting pesticide residues. [ABSTRACT FROM AUTHOR]

Na3V2(PO4)3 (NVP) with a NASICON structure serves as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to its stable crystal structure and fast ion mobility. Nevertheless, its electrochemical properties are still unsatisfactory because of its poor electrical conductivity. A simple hydrothermal method is used to prepare carbon-coated NVP (NVP-C) and N/S co-doped carbon-coated NVP (NVP-C-NS) composites. The results demonstrate that the NVP-C-NS composite exhibits superior capacity and rate capability. After 100 cycles at a high current density of 1000 mA g−1, the reversible capacity of the NVP-C-NS composite can reach 115 mA h g−1, while pure NVP-C is capable of achieving only 83 mA h g−1 at the same current density, and 94.8% of the capacity of the NVP-C-NS composite and only 90% of the NVP-C material are retained. The excellent electrochemical performance of the NVP-C-NS composite is mainly due to the high carbon content (13.08 wt% vs. NVP-C with 4.8 wt%.) and high conductivity (3.72 × 10−4 S cm−1vs. NVP-C with 1.20 × 10−4 S cm−1). The introduction of more active sites and defects after N/S doping and the increased specific surface area can provide a larger electrochemical contact surface for electrochemical reactions. Furthermore, the practicality of the NVP-C-NS//Zn battery is evaluated by lighting up LED bulbs. This work provides a reference for the development of Na3V2(PO4)3 as a cathode material for AZIBs. [ABSTRACT FROM AUTHOR]

The nano-scale spherical Na3V2(PO4)2F3 with a NASICON structure phase was prepared with a spray drying technique, and the bagasse in Guangxi, China was selected as the carbon source to prepare Na3V2(PO4)2F3/C. The optimal preparation conditions of the composite determined using thermogravimetry, X-ray diffraction, scanning electron microscopy and electrochemical testing were: a calcination temperature of 650 °C and a 20% carbon source. The Na3V2(PO4)2F3/C has obvious redox peaks, determined by cyclic voltammetry (CV), at 3.90 V and 3.75 V, 4.32 V and 4.15 V. These two pairs of redox peaks correspond to the escape/intercalation of the two pairs of Li+/Na+. Notably, compared with pure Na3V2(PO4)2F3, the specific discharge capacity of Na3V2(PO4)2F3/C-20%, which were used as a cathode material for lithium–sodium hybrid ion batteries, increased from 55 mA h g−1 to 125 mA h g−1, which was an improvement of twofold. [ABSTRACT FROM AUTHOR]

The nano-scale spherical Na 3 V 2 (PO 4 ) 2 F 3 with a NASICON structure phase was prepared with a spray drying technique, and the bagasse in Guangxi, China was selected as the carbon source to prepare Na 3 V 2 (PO 4 ) 2 F 3 /C. The optimal preparation conditions of the composite determined using thermogravimetry, X-ray diffraction, scanning electron microscopy and electrochemical testing were: a calcination temperature of 650 °C and a 20% carbon source. The Na 3 V 2 (PO 4 ) 2 F 3 /C has obvious redox peaks, determined by cyclic voltammetry (CV), at 3.90 V and 3.75 V, 4.32 V and 4.15 V. These two pairs of redox peaks correspond to the escape/intercalation of the two pairs of Li + /Na + . Notably, compared with pure Na 3 V 2 (PO 4 ) 2 F 3 , the specific discharge capacity of Na 3 V 2 (PO 4 ) 2 F 3 /C-20%, which were used as a cathode material for lithium-sodium hybrid ion batteries, increased from 55 mA h g -1 to 125 mA h g -1 , which was an improvement of twofold.