Wanlin Yang,Tongmin Xu,Chengkai Yang,Huarong Fan,Wenxuan Sun,Xinfeng Ma,Xin Wang,Yongzhu Fu
The development of high energy density Li-organosulfur batteries is severely hampered by the slow redox kinetics and the shuttle effect of polysulfides. Reasonably designing new electrocatalysts to accelerate the electrochemical conversion of various intermediates is an effective strategy to overcome the above challenges. Specifically, high entropy metal carbides/nanofibers (Mn 0.25 Co 0.25 Ni 0.25 Cu 0.25 Fe 2 )C/CNFs (HEC/CNFs) are prepared by electrospinning method and applied in lithium-phenyl tetrasulfide (Li-PTS) batteries. The HEC composition, featuring multiple randomly dispersed metal elements, modulates its d -band structure and expedites the redox reaction for polysulfides. Therefore, HEC as a bidirectional catalyst reduces the activation energy of the redox reaction and selectively regulates the improvement of the generation and decomposition of inorganic intermediates during the charge–discharge process. The HEC/CNFs/PTS electrodes have an initial theoretical specific capacity of 527 mAh g −1 at 0.5 C, with a slow capacity decay rate of 0.078% per cycle, exceeding 500 cycles. More importantly, it can also maintain a theoretical specific capacity of 450 mAh g −1 under high surface loading conditions (PTS ≈ 4.8 mg cm −2 ) when applied to Li-organosulfur pouch cells. This work demonstrates the bidirectional catalytic effect of HEC in Li-PTS batteries and presents pathways for energy storage and conversion in various high entropy carbide materials.
He Wang,Hongling Guo,Zihao Huang,Weiliang Liu,Mei Li,Jinshui Yao,Jiaxi Cui,Yuanhao Wang,Manman Ren
The high activity barriers of Li 2 S nucleation and deposition limit the redox reaction kinetics of lithium polysulfides (LiPSs), meanwhile, the significant shuttle effect of LiPSs hampers the advancement of Li-S batteries (LSBs). In this work, a NiSe 2 /CoSe 2 -rGO (NiSe 2 /CoSe 2 -G) sulfur host with bifunctional catalytic activity was prepared through a hard template method. Electrochemical experiment results confirm that the combination of NiSe 2 and CoSe 2 not only facilitates the bidirectional catalytic function during charge and discharge processes, but also increases the active sites toward LiPSs adsorption. Simultaneously, the highly conductive rGO network enhances the electronic conductivity of NiSe 2 /CoSe 2 -G/S and provides convenience for loading NiSe 2 /CoSe 2 catalysts. Benefitting from the exceptional catalytic-adsorption capability of NiSe 2 /CoSe 2 and the presence of rGO, the NiSe 2 /CoSe 2 -G/S electrode exhibits excellent electrochemical properties . At 1C, it demonstrates a low capacity attenuation of 0.087 % per cycle during 500 cycles. The electrode can maintain a discharge capacity of 927 mAh/g at a sulfur loading of 3.3 mg cm −2 . The bidirectional catalytic activity of NiSe 2 /CoSe 2 -G offers a prospective approach to expedite the redox reactions of active S, meanwhile, this work also offers an ideal approach for designing efficient S hosts for LSBs.
Distinct from most electrochemiluminescence sensors that rely on elaborate materials, this study develops an immunosensor using simple materials for low-cost and highly sensitive biological analysis. We elucidated the mechanism of paradoxical amplification of gold nanoparticles (AuNPs), designed strategies of bidirectional catalysis, and expanded the application for multibiomarker detection. First, a new understanding of AuNPs’ catalytic role was established through investigating the inhibitory effects of five phenolic compounds on the luminol–H2O2 ECL system, and an AuNP-induced “paradoxical amplification” of phenolic electrochemiluminescence (ECL) inhibition was first identified. Contrary to the common view that AuNPs always enhance ECL, here, AuNPs amplified the inhibitory effect of phenolics, thereby reducing the ECL signal. Such a mechanism was validated via electrochemistry-mass spectrometry. Second, a methodological innovation is presented: a switch-type immunosensor with bidirectional catalytic amplification via dynamic conversion. Specifically, the same catalyst flexibly switches between enhancement and inhibition: horseradish peroxidase (HRP) and AuNPs first act synergistically to enhance the initial ECL signal of the luminol–H2O2 system; then, alkaline phosphatase serves as a “switch” and introduces phenolic compounds, triggering HRP and AuNPs to automatically convert into signal-inhibiting catalysts. This induces multiple signal attenuation via ECL energy resonance transfer, radical quenching, and mass transfer hindrance, leading to a rapid decrease in ECL response. Finally, a highly sensitive coupled enzyme-linked attenuated ECL immunoassay involving AuNPs was constructed and successfully applied to the specific detection of cardiac troponin I and erythropoietin with a wide linear range (from fg/mL to ng/mL), and a detection limit as low as fg/mL.
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