Free-Standing, Self-Doped Porous Hard Carbon: Na-Ion Storage with Enhanced Initial Coulombic Efficiency.

The use of porous hard carbons (PHCs) as electrode materials in sodium-ion batteries has great potential; however, the exposure of large surface areas to electrolyte flow results in irregular and irreversible solid electrolyte interfaces (SEIs), leading to deteriorated ionic and electronic mobility and inferior initial Coulombic efficiency (ICE). These issues can be addressed through suitable structural modifications of PHC materials. Herein, the integration of high-surface-area PHCs with carbon nanofibers (CNFs) was accomplished by a simple electrospinning technique, which resulted in a uniform and reversible SEI layer. In the meantime, the CNFs' mesh provided connectivity and conductivity in the as-integrated electrodes, whereas PHCs offered fast diffusion kinetics and high Na+ ion storage capacity. Additionally, PHC integration with CNFs demonstrated an excellent ICE of 77% and a specific capacity of 505 mAh/g at 25 mA/g. Furthermore, the conjugated microstructure also provided flexibility and stability to the electrode (260 mAh/g after 500 cycles). This remarkable synergy may promote the development of free-standing, flexible, and highly porous properties in a single material for advanced energy storage applications.

Plasmonic Surface of Metallic Gold and Silver Nanoparticles Induced Fluorescence Quenching of Meso-Terakis (4-Sulfonatophenyl) Porphyrin (TPPS) and Theoretical-Experimental Comparable.

Colloidal metallic nanoparticles have attracted a lot of interest in the last two decades owing to their simple synthesis and fascinating optical properties. In this manuscript, a study of the effect of both gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) on the fluorescence emission (FE) of TPPS has been investigated utilizing steady-state fluorescence spectroscopy and UV-Vis spectrophotometry. From the observed electronic absorption spectra, there is no evidence of the ground state interaction between metallic Au NPs or Ag NPs with TPPS. On the other side, the FE spectra of TPPS have been quenched by both Ag and Au NPs. Via applying quenching calculations, Ag NPs showed only traditional static fluorescence quenching of TPPS with linear Stern-Volmer (SV) plots. On the contrary, quenching of TPPS emission by Au NPs shows composed models. One model is the sphere of action static quenching model that prevails at high quencher concentrations leading to non-linear SV plots with positive deviation. However, at low Au NPs concentrations, traditional dynamic quenching occurs with linear SV plots. The quantum calculations for TPPS structure have been obtained using Gaussian 09 software: in which the TPPS optimized molecular structure was achieved using DFT/B3LYP/6-311G (d) in a gaseous state. Also, the calculated electronic absorption spectra for the same molecule in water as a solvent are obtained using TD/M06/6-311G + + (2d, 2p). Furthermore, the theoretical and experimental results comparable to UV-Vis spectra have been investigated.

One-step sonochemical fabrication of biomass-derived porous hard carbons; towards tuned-surface anodes of sodium-ion batteries.

A facile one-step sonochemical activation method is utilized to fabricate biomass-derived 3D porous hard carbon (PHC-1) with tuned-surface and is compared with the conventional two-step activation method. As raw biomass offers good KOH impregnation, ultrasonication power diffuses both K+ and OH- ions deep into its interior, creating various nanopores and attaching copious functional groups. In contrast, conventional activation lacks these features under the same carbonization/activation parameters. The high porosity (1599 m2/g), rich functional groups (O = 8.10%, N = 0.95%), and well-connected nanoporous network resulting from sonochemical activation, remarkably increased specific capacity, surface wettability, and electrode stability, consequently improved electrochemical performance. Benefiting from its suitable microstructure, PHC-1 possesses superior specific capacity (330 mAh/g at 20 mA/g), good capacity retention (89.5%), and excellent structural stability over 500 sodiation/desodiation cycles at high current density (1000 mA/g). Apart from modus operandi comparison, the two activation methods also provide mechanistic insights as the low-voltage plateau region and graphitic layers decrease simultaneously. This work suggests a scalable and economical approach for synthesizing large-scale activated porous carbons that are used in various applications, be it energy storage, water purification, or gas storage, to name a few.

Electrospun carbon nanofibers with multi-aperture/opening porous hierarchical structure for efficient CO2 adsorption.

HYPOTHESIS: Carbonaceous materials are believed to be excellent source for developing essential vessels for carbon dioxide (CO2) adsorption. However, most of the carbonaceous materials used for CO2 capture have particle form, which is hard to recycle and also may cause choking of the gas pipes. Additionally, they also either require chemical activation or attachment of any functional groups for proficient CO2 capture. Thus, facile fabrication of multi-aperture porous carbon nanofiber (CNF) based CO2 sorbent via combination of three simple steps of electrospinning, washing, and carbonization, may be an effective approach for developing efficient sorbents for CO2 capture. EXPERIMENT: PAN/PVP composite solution was electrospun, PVP was used as pore forming template and PAN was opted as nitrogen rich precursor for carbon during electrospinning process. Selective removal of PVP from the electrospun PAN/PVP fiber matrix prior to carbonization generated highly rough and extremely porous PAN nanofibers, which were then carbonized to develop multi-aperture/opening porous carbon nanofibers (PCNF) with ultra-small pores with average pore diameter of ~0.71 nm. FINDINGS: Synthesized PCNF exhibited high CO2 gas selectivity (S = 20) and offered superior CO2 adsorption performance of 3.11 mmol/g. Moreover, no apparent change in mass for up to 50 cycles of CO2 adsorption/desorption unveil the long-term stability of synthesized PCNF, making them a potential candidate for CO2 adsorption application.

Sonochemical assisted fabrication of 3D hierarchical porous carbon for high-performance symmetric supercapacitor.

A scalable fabrication of 3D hierarchical porous carbon structure (3D-HPC) has been achieved via a simple sonochemical route at different pyrolysis temperatures. It is worth noting that all the 3D-HPC samples possess oxygen-functional groups after activation by KOH and self-doped by nitrogen, which are beneficial to improving their surface wettability as well as increasing the electro-active surface area between the electrode and the surrounding electrolyte, consequently enhancing their electrochemical performance. Remarkably, the resulting carbon sample pyrolyzed at 850 °C (AC-850) possesses a maximum doping level of 2.75 at% and a high surface area of 1376.19 m2 g-1, which exhibits high electrochemical performance with high capacitance up to 269.19 F g-1 at a current density of 2 A g-1. Moreover remarkably, the AC-850-based symmetric supercapacitor delivers a high energy density of 21.4 Wh kg-1 at a power density of 531.2 W kg-1 with excellent rate performance and superior cycling stability (94.7% retention over 5000 cycles). The present approach is very suitable for large scale production of high-quality porous carbon materials at low cost, which can be used in different aspects, such as energy storage, gas storage, environmental remediation, and so on.

Self-Assembled Porous-Silica within N-Doped Carbon Nanofibers as Ultra-flexible Anodes for Soft Lithium Batteries.

Silica is an attractive anode material for soft lithium batteries owing to its high specific capacity, but it suffers severe problems of large volume change and unstable solid-electrolyte interface. Moreover, it is a challenge to fabricate flexible silica anodes. Here, we report a low-cost and scalable strategy to create flexible anodes of N-doped carbon nanofiber-confined porous silica (p-SiO2@N-CNF) by developing a sol-gel electrospinning process followed by carbonization. This approach causes the p-SiO2 nanoparticles (NPs) to be self-assembled within the N-CNFs, which act like elastomer and electrolyte barrier to accommodate volume changes and to enhance the stability of SiO2, whereas the NPs act as soft plasticizer providing strength to the CNF skeletons. Benefiting from the hierarchical structures, the anodes with high p-SiO2 loadings (>1.6 mg/cm2) exhibit exceptional cycling performance (>1,000 cycles) in terms of bending, current rate, and capacity. Moreover, the batteries remain stable when discharging at 0.5 C and charging at 2 C.