Self-Supporting Carbon Nanofibers with Ni-Single-Atoms and Uniformly Dispersed Ni-Nanoparticles as Scalable Multifunctional Hosts for High Energy Density Lithium-Sulfur Batteries

Enhanced oxidase-mimic constructed by luminescent carbon dots loaded on MIL-53(Fe)-NO2 for dual-mode detection of gallic acid and biothiols in food and humans

Monitoring of gallic acid (GA) in food and biothiols in humans is crucial for body health. Nanozyme-mediated colorimetric strategy for evaluating them has been widely applied nowadays, however, the inferior efficient and susceptible single-signal recognition limit its further application. Herein, a sensitive biosensor was first constructed for bimodal detection of GA and biothiols based on CDs@MIL-53(Fe)-NO2, prepared through a facile and time-saving microwave treatment. Benefiting from the excellent fluorescent and electron transfer properties of CDs, CDs@MIL-53(Fe)-NO2 exhibited significant enhanced blue fluorescence and oxidase-like activity, which could oxide colorless 3,3',5,5'-tetramethylbenzidine without H2O2, and the blue product could quench the fluorescence of composite. The dual-mode assay based on such bifunctional nanozyme showed an extremely sensitivity towards GA/l-cysteine/homocysteine with the detection limit of 62/65/124 nM and 17/16/27 nM in colorimetric/fluorescent modes, respectively. The practicability in real samples and portability based on a smartphone of the analysis has been investigated with reliable results.

GO-CoNiP New Composite Material Modified Separator for Long Cycle Lithium-Sulfur Batteries

Lithium-sulfur batteries with high capacity are considered the most promising candidates for next-generation energy storage systems. Mitigating the shuttle reaction and promoting catalytic conversion within the battery are major challenges in the development of high-performance lithium-sulfur batteries. To solve these problems, a novel composite material GO-CoNiP is synthesized in this study. The material has excellent conductivity and abundant active sites to adsorb polysulfides and improve reaction kinetics within the battery. The initial capacity of the GO-CoNiP separator battery at 1 C is 889.4 mAh g-1 , and the single-cycle decay is 0.063% after 1000 cycles. In the 4 C high-rate test, the single-cycle decay is only 0.068% after 400 cycles. The initial capacity is as high as 828.2 mAh g-1 under high sulfur loading (7.3 mg cm-2 ). In addition, high and low-temperature performance tests are performed on the GO-CoNiP separator battery. The first cycle discharge reaches 810.9 mAh g-1 at a low temperature of 0 °C, and the first cycle discharge reaches 1064.8 mAh g-1 at a high temperature of 60 °C, and both can run stably for 120 cycles. In addition, in situ Raman tests are conducted to explain the adsorption of polysulfides by GO-CoNiP from a deeper level.

Boosting Lean Electrolyte Lithium-Sulfur Battery Performance with Transition Metals: A Comprehensive Review

Lithium-sulfur (Li-S) batteries have received widespread attention, and lean electrolyte Li-S batteries have attracted additional interest because of their higher energy densities. This review systematically analyzes the effect of the electrolyte-to-sulfur (E/S) ratios on battery energy density and the challenges for sulfur reduction reactions (SRR) under lean electrolyte conditions. Accordingly, we review the use of various polar transition metal sulfur hosts as corresponding solutions to facilitate SRR kinetics at low E/S ratios (< 10 µL mg-1), and the strengths and limitations of different transition metal compounds are presented and discussed from a fundamental perspective. Subsequently, three promising strategies for sulfur hosts that act as anchors and catalysts are proposed to boost lean electrolyte Li-S battery performance. Finally, an outlook is provided to guide future research on high energy density Li-S batteries.

Ultrafine Co-Species Interspersed g-C3N4 Nanosheets and Graphene as an Efficient Polysulfide Barrier to Enable High Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the promising advanced energy storage systems due to their ultrahigh capacity and energy density. However, their practical applications are still hindered by the serious shuttle effect and sluggish reaction kinetics of soluble lithium polysulfides. Herein, g-C₃N₄ nanosheets and graphene decorated with an ultrafine Co-species nanodot heterostructure (Co@g-C₃N₄/G) as separator coatings were designed following a facile approach. Such an interlayer can not only enable effective polysulfide affinity through the physical barrier and chemical binding but also simultaneously have a catalytic effect on polysulfide conversion. Because of these superior merits, the Li-S cells assembled with Co@g-C₃N₄/G-PP separators matched with the S/KB composites (up to ~70 wt% sulfur in the final cathode) exhibit excellent rate capability and good cyclic stability. A high specific capacity of ~860 mAh g^-1 at 2.0 C as well as a capacity-fading rate of only ~0.035% per cycle over 350 cycles at 0.5 C can be achieved. This bifunctional separator can even endow a Li-S cell at a low current density to exhibit excellent cycling capability, with a capacity retention rate of ~88.4% at 0.2 C over 250 cycles. Furthermore, a Li-S cell with a Co@g-C₃N₄/G-PP separator possesses a stable specific capacity of 785 mAh g^-1 at 0.2 C after 150 cycles and a superior capacity retention rate of ~84.6% with a high sulfur loading of ~3.0 mg cm^-2. This effective polysulfide-confined separator holds good promise for promoting the further development of high-energy-density Li-S batteries.

Nickel-Doped Carbon Dots as an Efficient and Stable Electrocatalyst for Urea Oxidation

Urea is a typical contaminant present in wastewater which may cause severe environmental problems. Electrochemical catalytic oxidation of urea has emerged as an efficient approach to solve this problem. Nevertheless, the current nickel-based catalysts (e.g., nickel hydroxide/sulfides) feature a high metal content. It not only lowers the utilization efficiency of nickel but also causes secondary pollution to the environment. Here, nickel-doped carbon dots (Ni-CDs) with an excellent and stable catalytic activity for the electrocatalytic urea oxidation reaction (UOR) are reported. Specifically, carbon dots (CDs) with abundant functional groups are synthesized by a one-pot hydrothermal method and then Ni-CDs with a very low metal content (1.1 at%) are prepared. The Ni²⁺ sites by coordination with carboxylic groups on the CDs provide excellent electrocatalytic activity and excellent durability for the UOR, as demonstrated by an anodic current density of 100 mA cm^-2 at a potential of 1.38 V (vs RHE) and similar experimental results in practical application. To the best of knowledge, this is the first report of CDs-based materials applied for the UOR, which opens an important new area of applicability for CDs as well as broadens the scope of the materials for electrochemical catalysis of urea.

Internal dual-emissive carbon dots for double signal detection of procainamide

We fabricated an internal dual-emission carbon dots using a facile hydrothermal treatment of eosin Y and ethylenediamine (EDA). The Y-CDs exhibit distinct double peaks at 384 and 520 nm on...