Polyacrylonitrile-based electrospun carbon paper for electrode applications

Polyacrylonitrile (PAN)-based carbon paper with fiber diameters of 200–300 nm was developed through hot-pressing, pre-oxidation, and carbonization of electrospun fiber mats. Changes in morphology, crystallinity, and surface chemistry of the hot-pressed carbon paper were investigated. More junctions between fibers were formed with increasing hot-press time, which is attributed to melting and bonding of fibers. The bulk density increased to 0.5–0.6 g/cm[superscript 3], which could help to improve the volume energy density for electrode applications. The conductivity of the carbon paper was found to be about 40 S/cm when the surface area was ∼ 2 m[superscript 2]/g, and depends not only on the conductivity of the individual nanofibers but also on the contacts between the nanofibers. The performance of the electrospun carbon paper as an electrode for electrochemical reactions involving ferrocene molecules was affected by the preparation protocol: the higher surface area of the electrodes formed with shorter hot-press times provided a higher current generated per unit mass than that obtained with electrodes prepared using longer hot-press time, but electrodes prepared with longer hot-press times exhibited higher electrical conductivity and faster electron transfer kinetics

An Electrochemically-mediated Gas Separation Process for Carbon Abatement

This work describes a promising alternative to conventional thermal processes for absorber/desorber processing of for removal of CO[subscript 2] from flue gas streams at fossil fuel fired power plants. Our electrochemically-mediated amine regeneration (EMAR) process offers the advantages of an electrical system coupled with the desirable high output purities typical of amine sorbents that are difficult to achieve with most electric systems such as pressure-swing sorption, membrane separation, and oxy-fuel combustion. Preliminary experimental results are presented that demonstrate the feasibility of using ethylenediamine as the CO[subscript 2] sorbent and copper electro-cycling to isothermally modulate the amine affinity for CO[subscript 2]. Cupric ions entirely deactivate ethylenediamine at a ratio of 2:1 diamine to copper. Open-circuit potential measurements at 50°C indicate the required energy to desorb CO[subscript 2] and regenerate the ethylenediamine is 18 kJ/mole CO[subscript 2] under open-circuit conditions. Kinetic over-potentials are sufficiently low to ensure acceptable energy losses. Lower energies can be achieved by increasing the temperature or by changing the amine.Siemens Corporation (CKI Research Fund)United States. Advanced Research Projects Agency-Energy (Research Grant DE-AR0000083

Post-combustion carbon dioxide capture using electrochemically mediated amine regeneration

Electrochemically mediated amine regeneration is a new post-combustion capture technology with the potential to exploit the excellent removal efficiencies of thermal amine scrubbers while reducing parasitic energy losses and capital costs. The improvements result from the use of an electrochemical stripping cycle, in lieu of the traditional thermal swing, to facilitate CO[subscript 2] desorption and amine regeneration; metal cations generated at an anode react with the amines, displacing the CO[subscript 2], which is then flashed off, and the amines are regenerated by subsequent reduction of the metal cations in a cathode cell. The advantages of such a process include higher CO[subscript 2] desorption pressures, smaller absorbers, and lower energy demands. Several example chemistries using different polyamines and copper are presented. Experimental results indicate an open-circuit efficiency of 54% (15 kJ per mole CO[subscript 2]) is achievable at the tested conditions and models predict that 69% efficiency is possible at higher temperatures and pressures. A bench scale system produced 1.6 mL min[superscript −1] CO[subscript 2] while operating at 0.4 volts and 42% Faradaic efficiency; this corresponds to a work of less than 100 kJ per mole.United States. Advanced Research Projects Agency-Energy (Grant DE-AR0000083

Metallocene/carbon hybrids prepared by a solution process for supercapacitor applications

Efficient and scalable solution-based processes are not generally available to integrate well-studied pseudocapacitive materials (i.e., metal oxides and conducting polymers) with other components such as porous carbon, mainly because these classes of pseudocapacitive systems have poor solubilities in solvents and exhibit no specific interactions with the other component. Here we report, for the first time, the integration of a metallocene polymer, polyvinylferrocene (PVF), with carbon nanotubes (CNTs) via a simple solution process for supercapacitor applications. The solution processability of the PVF/CNT hybrid is due to the high solubilities of PVF in organic solvents and the unique ability of the metallocene/carbon system to form stable dispersions through the π–π stacking interactions between the two components. The nanostructure and electrochemical properties of the hybrid can be manipulated systematically by adjusting the composition of the dispersion. The hybrid with the optimized composition exhibits unusually high capacitance (1452 F g[superscript −1]) and energy density (79.5 W h kg[superscript −1]) obtained in a standard two-electrode configuration, outperforming previously reported pseudocapacitive materials.United States. Dept. of EnergyMIT Energy Initiative (Seed Fund Grant

Electrochemically mediated separation for carbon capture

Carbon capture technology has been proposed as an effective approach for the mitigation of anthropogenic CO[subscript 2] emissions. Thermal-swing separation technologies based on wet chemical scrubbing show potential for facilitating CO[subscript 2] capture at industrial-scale carbon emitters; however, the total operational and capital costs resulting from the high energy consumption are prohibitive for their implementation. Electrochemically mediated processes are proposed to be the next generation of CO[subscript 2] separation technology that can enable carbon capture to be a more viable option for carbon mitigation in the near future. This technology utilizes electrochemically active sorbents that undergo significant changes in their molecular affinity for CO[subscript 2] molecules as they progress through an electrochemical cycle. This nearly isothermal separation process consumes electrical energy to facilitate effective CO[subscript 2] capture and regeneration processes under more benign conditions of sorption and desorption than in traditional continuous wet-scrubber operations. This electrically driven separation process has the potential to significantly reduce the difficulty of retrofitting CO[subscript 2] capture units to existing fossil fuel-fired power generators. The ease of installing an electrically driven separation system would also allow its application to other industrial carbon emitters. The design of such a system, however, requires careful consideration since it involves both heterogeneous electrochemical activation/deactivation of sorbents and homogeneous complexation of the activated sorbents with CO[subscript 2] molecules. Optimization of the energy efficiency requires minimizing the irreversibility associated with these processes. In this study, we use a general exergy analysis to evaluate the minimum thermodynamic work based on the system design and the electrochemical parameters of quinodal redox-active molecules. Using this thermodynamic framework, our results suggest that the proposed technology could capture CO[subscript 2] from a dilute post-combustion flue gas and regenerate CO[subscript 2] at 1 bar with high efficiency, if a two-stage design is effectively implemented.Siemens Corporation (Massachusetts Institute of Technology. Center of Knowledge Interchange Project Fund

Aggregation of Synthetic Gene Delivery Vectors Enhance the Cellular Association and Uptake for in vitro Transfection

Development of safe and efficient synthetic gene delivery vectors is hampered with limited understanding the fundamental correlation of physicochemical properties of the vectors with their biological activities. Five major barriers contributing to poor transfection efficiency of synthetic vectors include cellular association, endosomal escape, intracellular trafficking, nuclear translocation and transcription of exogenous genes. In this study, the correlation of physicochemical properties of polymer-based synthetic gene delivery vectors (polyplexes) with cellular association as the first barrier for in vitro transfection was investigated. Polyethylene oxide block copolymer with poly(2-(dimethylamino)ethyl methacryate) (PEO-b-pDMAEMA) was chosen as the model in this study. Cellular association and transfection efficiency of block copolymer complexes were studied in Neuro2A cells. Quantitative real time polymerase chain reaction (PCR) was applied to elucidate the cellular association of polyplexes. Physicochemical properties of the vectors including size and surface charge were characterized using light scattering measurements. Formation of aggregate was found as the major indication for high cellular association and uptake for in vitro transfection.Singapore-MIT Alliance (SMA

Multi-messenger searches via IceCube’s high-energy neutrinos and gravitational-wave detections of LIGO/Virgo

We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo\u27s GWTC-2 catalog using IceCube\u27s neutrino triggers. We did not find any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event

In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p