Electrocatalytic Functionalized Specialty Paper as Low-Cost Porous Transport Layer Material in CO2-Electrolysis

The development of low-cost and efficient electrolyzer components is crucial for practical electrochemical carbon dioxide reduction (ECR). In this study, facile non-woven cellulose-based porous transport layers (PTLs) were developed for high current density CO₂-to-CO conversion. By depositing a cobalt phthalocyanine (CoPc) catalyst-layer over the PTLs, we fabricated ECR-functioning gas-diffusion-electrodes (GDEs) for both flow-cell and zero-gap electrolyzers. Under optimal conditions, the Faradaic efficiency of CO (FE_CO) reached 92 % at a high current density of 200 mA cm⁻². Furthering the architecture of the GDEs, CoPc was incorporated into the initial PTL slurry, forming ECR-active PTLs without the need for an additional catalyst-layer. The new GDE-architecture favored the CoPc-distribution by enhancing the contact and interactions with the carbon substrate and demonstrated a stable electrolysis process for over 50 h in a zero-gap cell at 200 mA cm⁻² with a FE_CO of 80 %.     

LiCoO2电池正极微结构重构及有效传输系数预测

采用Monte Carlo方法重构了LiCoO2电池正极的三维微结构,重构单元的特征尺寸为几十纳米量级,从而得到了明确区分活性材料、固体添加物以及孔相(电解液)的微结构.通过对重构电极的特征化分析,得到了微结构中特定相的连通性和扭曲率、组分体积分数的空间分布、比表面积、孔径分布等特征信息.采用D3Q15格子Boltzmann模型(LBM)计算了该重构电极的有效热导率、电解液(或固相)的有效传输系数.同时发现,与随机行走方法以及Bruggemann关系式计算获得的扭曲率数值相比,LBM预测值更可靠.     

Transport properties of uniaxially oriented aliphatic polyketone

The oxygen, carbon dioxide, and water‐transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5–10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X‐ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress‐strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw‐induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30–40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen‐bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 947–955, 2004     

In operando synchrotron X-ray radiography studies of polymer electrolyte membrane water electrolyzers

Polymer electrolyte membrane water electrolysis (PEL) cells are studied in-operando by synchrotron X-ray radiography. Two-phase flow phenomena associated with the evolution of oxygen and hydrogen in the surrounding water are investigated on a running electrolyzer cell. We examine the gas bubble discharge from the porous transport layer (PTL) into the flow channel and discuss the transport of bubbles in the flow channel. The transport of gas inside the PTL and the number of gas bubble discharge sites is examined and correlated with current density.     

Transport and Reaction Characteristics of Reconstructed Polyolefin Particles

The 3D spatial structure of porous polyethylene particles was reconstructed from their X‐ray micro‐tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully‐developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures.

     

Structural and Electrosurface Properties of Iron-Containing Porous Glasses in NaCl Solutions. I. Structural and Transport Characteristics of Porous Glasses

The structural (structural resistance coefficient, volume porosity, average pore radius, and specific surface area) and transport (specific electrical conductivity and counterion transport numbers) characteristics of high-silica micro- and macroporous glasses with different compositions (magnetite-free and magnetite- containing glasses) have been compared in solutions of an indifferent electrolyte (sodium chloride). It has been shown that the incorporation of iron(III) oxide into basic sodium-borosilicate glass changes the structure of the pore space of both microporous glasses produced by acidic leaching and macroporous glasses obtained from the microporous samples by additional alkaline treatment. Moreover, it has been found that the transport characteristics of microporous glasses with different compositions are similar, while, for magnetite- phase-containing macroporous glasses, the specific conductivity of a pore solution and counterion transport numbers are increased.     

Structural and Transport Properties of Alumina Porous Membranes from Process-Based and Statistical Reconstruction Techniques

We study the structural and transport properties of two model porous membranes made by compaction of spherical monosize gamma-alumina particles. A ballistic deposition process of spherical particles has been employed as a process-based representation method for accurately simulating the pore structure of the membranes. Comparison between the computed and experimental permeability values obtained in the Knudsen regime shows very good agreement for both membranes and indicates that sufficient representation of the original pore structure is achieved with the random sphere packs. In a further step, a medium with the same porosity and autocorrelation function as the sphere pack has been stochastically reconstructed. Comparison between the structural properties of the random sphere pack system (process-based model) and the stochastically reconstructed medium (statistical model) shows nearly identical correlation functions and pore chord length distributions but widely different mass chord length distributions. This is reflected to a significant difference in the prediction of a dynamic property like the Knudsen permeability by a factor of about 4. The results suggest that matching of the porosity and the two-point correlation function alone is not always adequate when pursuing an accurate representation of the structure of a porous material. In such cases, higher order statistical properties of the material contained in the chord length distribution of both pore and solid phase should be satisfied as well. It is also found that proper account of the formation process in the reconstruction of a porous material (process-based model) leads to representations of its structure more accurate than those of statistical reconstruction models. Copyright 2000 Academic Press.     

Effect of fiber orientation,stress state and notch radius on the impact properties of short glass fiber reinforced polypropylene

Short glass fiber reinforced polypropylene (sgf-PP) is increasingly used in the automotive industry with the impact properties as key parameter. Experimentally, the impact behavior strongly depends on the specimen design, test set-up as well as temperature, and thus the characterization method should always be attuned to the occurring impact conditions of the final part. However, in order to deduce some general design criteria for sgf-PP, in this study a wide range of experimental parameters were investigated, specially focusing also on the effect of the governing, local fiber orientation distribution (FOD). Therefore, the effects of stress state (tensile, puncture and bending test), amount of stress concentration (notch radius) and temperature are characterized and discussed. The results proved that, as expected, distinctly different levels of impact strength and different dependencies on notches and notch radii are obtained for the various test set-ups. However, similarities in the temperature dependence are observed for specimens with similar governing fiber orientation.     

Facilitated Transport of Molecular Oxygen in Membranes of Macromolecular Cobalt-Porphyrin Complex: Modification of Dual-Mode Transport Model

Transport of molecular oxygen is facilitated in poly(butyl methacrylate) membranes containing the cobalt(II)-α,α′,α″,α′″-meso-tetrakis(o-pivalamidophenyl)porphyrin-1-methylimidazole (CoPIm) complex which forms oxygen adduct rapidly and reversibly. The facilitated transport of oxygen is studied by modifying a dual-mode transport model for gas permeation. The diffusion coefficient of oxygen via the fixed CoPIm complexes (Langmuir mode) is assumed to depend on oxygen concentration, and the modified dual-mode transport equation is described for the permeation steady state. The modified equation represents the effect of upstream oxygen pressure on the permeability. The oxygen permeation behavior through the macromolecular-metal complex membrane is discussed.     

Use of Liquid Precursors for Diamond Chemical Vapor Deposition--The Effects of Mass Transport and Oxygen

Thermal plasma chemical vapor deposition of diamond-utilizing liquidfeedstock injection has been shown to yield higher mass deposition rates,larger crystal size, and thicker films when compared to the use of gaseousfeedstock for equivalent operating conditions. Increased mass transport ofthe activated precursor species across the substrate diffusion boundarylayer and the presence of oxygen in liquid precursors are investigated aspotential reasons for the observed results. Comparisons of the variousprecursor systems investigated in this study are based on crystal size andfilm thickness as a function of radial postion, area of deposit, totalmass deposition rate, and the observed liquid precursor droplet trajectorieswithin the deposition chamber using a laser strobe video system. The resultsindicate that the mass transport in both the liquid and gaseous precursorsystems is greatly improved by the use of an inert carrier gas. Further, theuse of a liquid versus a gaseous precursor does not seem toresult in higher total deposition rates when the operating conditions forboth have been optimized. Finally, the presence of oxygen in the liquidfeedstock system is found to be at least partly responsible for theincreased growth rate, which is observed when comparing the plainhydrocarbon precursor cases with the oxygenated liquid precursorcase.     

Effects of Electrolytes on the Transport Phenomena in a Cation-Exchange Membrane

The effect of electrolyte solutions on the characteristics of the current-voltage (I-V) curve in a cation-exchange membrane (CMX membrane, Tokuyama Soda, Inc.) was studied based on the concentration polarization and electroconvection theory. The study includes the limiting current density (LCD), plateau length, and the ratio of resistance of region III to region I of the I-V curve (R(3rd)/R(1st)). Different electrolyte solutions, HCl, LiCl, NaCl, KCl, CaCl(2), MgCl(2), and AlCl(3), were used in this study. The LCD values of the electrolytes were correlated with the diffusion coefficient of the cation (D(+)) and valence of the cation and anion (z(+), z(-)). Except for the HCl solution, the LCD values of the electrolytes increased linearly with D(+)(1-z(+)/z(-)), implying that the current in this region was governed by the concentration polarization phenomena. The deviation of the HCl solution from the linearity is due to a particular transport mechanism of the proton called the Grotthuss-type transport. The differences in the plateau length and the resistance ratio, R(3rd)/R(1st), with the electrolytes were explained by the Péclet number (Pe) representing a transport pattern in the electroconvection theory. The Péclet number is proportional to the Stokes radius of an ion. An electrolyte with a large Stokes radius has a shorter plateau length and a lower ratio of R(3rd)/R(1st) than those of an electrolyte with a small Stokes radius. Water-splitting measurements for the different electrolyte solutions in the CMX membrane revealed that the contribution of water splitting to the overlimting current was insignificant regardless of the electrolytes used in this study. However, when metal hydroxides, such as Al(OH)(3), formed on the surface of the membrane, significant water splitting was observed. Copyright 2001 Academic Press.     

INVESTIGATION OF PROTRIPTYLINE PHOTOPRODUCTS WHICH CAUSE CELL MEMBRANE DISRUPTION

Abstract— Protriptyline (PTL; N-methyl-5H-dibenzo[a,d]cycloheptene-5-propylamine) hydrochloride is a skin photosensitizing agent in humans. The fluorescence and photochemical behavior of PTL varies with the solvent. In water, 40% ethanol and ethanol in the hydrochloride salt of PTL has a fluorescence quantum yield of 0.81. The fluorescence quantum yield of PTL free base in selected organic solvents is between 0.41 and 0.17; in ethanol it remains at 0.81. Photolysis of PTL in acidic aqueous solution yields at least five photoproducts which were separated by high-performance liquid chromatography. Three of these photoproducts lysed red blood cells. One of the photoproducts has been identified as a cyclobutyl photodimer of PTL based on its mass spectrum and UV absorption and its ability to undergo photore-versal with 254 nm irradiation. The others were not cyclobutyl dimers. The yield of lytic products decreased as the ethanol content was increased and were not formed from PTL free base in any solvent.     

Electrochemical stripping with carbon fiber electrodes in a microliter-capacity cell

The construction of a microcell with an in-situ mercury-plated carbon fiber electrode for the application of electrochemical stripping techniques is described. The performance of the cell is compared to a conventional mercury-film glassy carbon electrode in large-volume cells with special emphasis on the effects of mass transport and oxygen interference. Effective mass transport is provided withouth forced convection and oxygen does not appear to influence the response of the carbon fiber electrode. The dependence of the a.s.v. and p.s.a. signals on the deposition time with the microcell deviated from linearity at deposition times above 3 min because of depletion effects and decreased concentration of oxidizing agent, respectively. Good reproducibility of lead determinations in the μg 1^?1 range by a.s.v. and p.s.a. was achieved in successive scans at the same fiber and in consecutive tests of identical samples. Calibration plots were linear in the 0.01–10 mg 1^?1 range. Sample volumes down to 5 μl were used in determining cadmium and lead. The detection limits for both elements obtained with a.s.v. and p.s.a. after 5-min preconcentration were 1 and 3 μg1^?1, respectively, or in absolute mass 5 pg and 15 pg, respectively.     

Tracking Ion Transport in Nanochannels via Transient Single-Particle Imaging

The transport behavior of ions in the nanopores has an important impact on the performance of the electrochemical devices. Although the classical Transmission-Line (TL) model has long been used to describe ion transport in pores, the boundary conditions for the applicability of the TL model remain controversial. Here, we investigated the transport kinetics of different ions, within nanochannels of different lengths, by using transient single-particle imaging with temporal resolution up to microseconds. We found that the ion transport kinetics within short nanochannels may deviate significantly from the TL model. The reason is that the ion transport under nanoconfinement is composed of multi basic stages, and the kinetics differ much under different stage domination. With the shortening of nanochannels, the electrical double layer (EDL) formation would become the “rate-determining step” and dominate the apparent ion kinetics. Our results imply that using the TL model directly and treating the in-pore mobility as an unchanged parameter to estimate the ion transport kinetics in short nanopores/nanochannels may lead to orders of magnitude bias. These findings may advance the understanding of the nanoconfined ion transport and promote the related applications.     

聚合物-卟啉钴复合膜的氧气促进输送性能

综述了聚合物－卟啉钴复合膜的氧气促进输送性能。讨论了卟啉钴的结构及与氧的结合性能，聚合物－卟啉钴复合膜的氧气促进输送特性，影响聚合物－卟啉钴复合膜氧气透过性能的因素及卟啉钴的不可逆氧化反应机理。     

Multiobjective Optimization of Fabrication Parameters of Jute Fiber/Polyester Composites with Egg Shell Powder and Nanoclay Filler

In the present study, a model is presented to optimize the fabrication parameters of natural fiber reinforced polyester matrix composites with dual fillers. In particular, jute fiber mat was chosen as reinforcement and eggshell powder (ESP) and montmorillonite nanoclay (NC) were selected as fillers. The weight per square meter (GSM) of the fiber, the weight percentage of ESP and NC have been chosen as independent variables and the influence of these variables on tensile, flexural and impact strength of the composite has been inspected. The permutations of the different combinations of factors are intended to accomplish higher interfacial strength with the lowest possible number of tested specimens. The experiments were designed by the Taguchi strategy and a novel multi-objective optimization technique named COPRAS (COmplex PRoportional ASsessment of alternatives) was used to determine the optimal parameter combinations. Affirmation tests were performed with the optimal parameter settings and the mechanical properties were evaluated and compared. Experimental results show that fiber GSM and eggshell powder content are significant variables that improve mechanical strength, while the nanoclay appears less important.     

Study of experimental and theoretical procedures when using thermogravimetric analysis to determine kinetic parameters of carbon black oxidation

Combustion of carbon black (CB) in the crucible of a thermobalance is controlled by both carbon reactivity and oxygen transport from the oxidizing flux to the surface of the bed and within the porous bed. The kinetic constant of combustion has been determined using a fixed-bed reactor in which CB combustion is mainly under kinetic control. Then, modelling of oxygen transport in the thermobalance allowed determining the oxygen diffusivity within the CB pile. Fickian diffusion is a good approximate value of the diffusion coefficient for modelling of internal oxygen transport. The effects of the initial sample mass and of the sample containment on the initial combustion rate have been investigated. The effectiveness factor of the bed was calculated for different experimental conditions. Advices to correctly extract a kinetic constant from thermogravimetric experiments are given. According to the required precision, an experimental procedure is proposed. Limitations to oxygen transport within the bed may be ignored. They can be minimized by the use of an inert material to remove the stagnant atmosphere between the surface of the bed and the mouth of the crucible. It appears mandatory to account for oxygen transport limitations within the CB pile. It can be assumed that the sample temperature (not known) during reaction is the regulation temperature. Thermal effects are also minimized by use of the inert material. A 30–50 mg sample mass seems to be optimal for determination of the kinetic parameters.     

Use of polymer fiber stationary phases for liquid chromatography separations: Part I--Physical and chemical rationale

The idea of using polymer fibers as stationary phases for LC is not a new one. There are in fact a number of good reasons for which they should be considered. To this point though, they have not produced sufficiently good performance to garner much commercial interest. Presented here are the physical and chemical rationale by which they should show enhanced performance relative to conventional stationary phases. Most notably, the mass transport and hydrodynamic characteristics suggest applications in areas of macromolecule and prep-scale separations. Additionally, there exists an incredible wealth of polymer surface chemistries and potential derivatization pathways that greatly exceed what is practical on conventional silica supports. The potential for important impact suggests further research into polymer fiber phases.