Boosting Bulk Oxygen Transport with Accessible Electrode Nanostructure in Low Pt Loading PEMFCs.

Despite the high potential for reducing carbon emissions and contributing to the future of energy utilization, polymer electrolyte membrane fuel cells (PEMFCs) face challenges such as high costs and sluggish oxygen transport in cathode catalyst layers (CCLs). In this study, the impact of pore size distribution on bulk oxygen transport behavior is explored by introducing nano calcium carbonate of varying particle sizes for pore-forming. Physicochemical characterizations for are employed to examine the electrode structure, while in situ electrochemical measurements are used to scrutinize bulk oxygen transport resistance, effective oxygen diffusivity ( D O 2 eff $D_{{{\mathrm{O}}}_2}^{{\mathrm{eff}}}$ ) and fuel cell performance. Additionally, the CCLs are constructed with aid of Lattice Boltzmann method (LBM) simulations and D O 2 eff $D_{{{\mathrm{O}}}_2}^{{\mathrm{eff}}}$ for CCLs with different pore size distribution are calculated. The findings reveal that D O 2 eff $D_{{{\mathrm{O}}}_2}^{{\mathrm{eff}}}$ initially increases and then decreases as the most probable pore size increases. A "sphere-pipe" model is proposed to describe practical bulk oxygen transport in CCLs, highlighting the significant role of not only the pore size of secondary pores but also the number of primary pores in bulk oxygen transport.

Tailored Porous Transport Layers for Optimal Oxygen Transport in Water Electrolyzers: Combined Stochastic Reconstruction and Lattice Boltzmann Method.

The porous transport layer (PTL) plays an integral role for the mass transport in polymer electrolyte membrane (PEM) electrolyzers. In this work, a stochastic reconstruction method of titanium felt-based PTLs is applied and combined with the Lattice Boltzmann method (LBM). The aim is to parametrically investigate the impact of different PTL structures on the transport of oxygen. The structural characteristics of a reconstructed PTL agree well with experimental investigations. Moreover, the impact of PTL porosity, fiber radius, and anisotropy parameter on the structural characteristics of PTLs are analyzed, and their impact on oxygen transport are elucidated by LBM. Eventually, a customized graded PTL is reconstructed, exhibiting almost optimal mass transport performance for the removal of oxygen. The results show that a higher porosity, larger fiber radius, and smaller anisotropy parameter facilitate the formation of oxygen propagation pathways. By tailoring the fiber characteristics and thus optimizing the PTLs, guidelines for the optimal design and manufacturing can be obtained for large-scale PTLs for electrolyzers.

New method for measuring the pore sizes and pore size distributions of filter membranes-the fluorescence probe method.

A novel, simple, and rapid method is demonstrated for measuring the pore size and pore size distribution of filtration membranes (FMs) used in aqueous applications with fluorescence probes. Because the selected fluorescent probes are mixable and have strong signals, combined with the operation of dead-end filtration, this method only requires small amounts of reagents; additionally, it is time-efficient by avoiding multiple rounds of filtration. This method detects the size of a FM pore throat (i.e., the narrowest position of a pore tunnel), which is more consistent with the actual filtration situation. The conditions, such as probe concentration, temperature, transmembrane pressure difference, and types of surfactants, have been optimized. The experimental results show that the fluorescence probe method has good accuracy and reproducibility for measuring the pore size and pore size distribution of both organic and inorganic FMs. The method is particularly suitable for rapid testing of the filtration performance (nominal pore size≥0.02 µm) of purchased or synthetic membranes in the laboratory.

Impact of Polymer Chain Rearrangements in the PA Structure of RO Membranes on Water Permeability and N-Nitrosamine Rejection.

The use of solvents is overall recognized as an efficient method to improve the water permeability of polyamide thin film composite membranes (PA-TFC). The objective of this work was to test the performance of the membranes after exposing them to n-propanol (n-PrOH) to improve the permeability of the membranes while maintaining the rejection factor for small uncharged organic molecules, namely N-nitrosamines (NTRs). After the membranes were exposed to n-PrOH, the water permeability of the UTC73AC membrane increased by 98%, with minimal change in rejection. N-nitrosodiethylamine (NDEA) rejection decreased (3.4%), while N-nitrosodi-n-propylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) rejection increased by 0.9% and 2.8%, respectively. In contrast, for the BW30LE membrane, water permeability decreased (by 38.7%), while rejection factors increased by 14.5% for NDEA, 6.2% for NDPA, and 15.0% for NDBA. In addition, the morphology of the membrane surface before and after exposure to n-PrOH was analyzed. This result and the pore size distribution (PSD) curves obtained indicate that the rearrangement of polymer chains affects the network or aggregate pores in the PA layer, implying that a change in pore size or a change in pore size distribution could improve the permeability of water molecules, while the rejection factor for NTRs is not significantly affected.

Effect of Pore Size Distribution on Energy Storage of Nanoporous Carbon Materials in Neat and Dilute Ionic Liquid Electrolytes.

This study investigates three carbide-derived carbon (CDC) materials (TiC, NbC, and Mo2C) characterized by uni-, bi-, and tri-modal pore sizes, respectively, for energy storage in both neat and acetonitrile-diluted 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A distribution of micro- and mesopores was studied through low-temperature N2 and CO2 adsorption. To elucidate the relationships between porosity and the electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were conducted using three-electrode test cells. The ultramicroporous TiC-derived carbon is characterized by a high packing density of 0.85 g cm-3, resulting in superior cathodic and anodic capacitances for both neat ionic liquid (IL) and a 1.9 M IL/acetonitrile electrolyte (93.6 and 75.8 F cm-3, respectively, in the dilute IL). However, the bi-modal pore-sized microporous NbC-derived carbon, with slightly lower cathodic and anodic capacitances (i.e., 85.0 and 73.7 F cm-3 in the dilute IL, respectively), has a lower pore resistance, making it more suitable for real-world applications. A symmetric two-electrode capacitor incorporating microporous CDC-NbC electrodes revealed an acceptable cycle life. After 10,000 cycles, the cell retained approximately 75% of its original capacitance, while the equivalent series resistance (ESR) only increased by 13%.

Assessment of density functional approximations for N2 and CO2 physisorption on benzene and graphene.

Experimental isotherms of N2 and CO2 on carbon-based porous materials and models of the physisorption of gases on surfaces are used to obtain the pore size distribution (PSD). An accurate modelization of the physisorption of N2 and CO2 on the surface of carbon-based porous materials is important to obtain accurate N2 and CO2 storage capacities and reliable PSDs. Physisorption depends on the dispersion interactions. High precision ab initio methods, such as CCSD(T), consider accurately the dispersion interactions, but they are computationally expensive. Double hybrid, hybrid and DFT-based methods are much less expensive. In the case of graphene, there are experimental data of the adsorption of N2 and CO2 on graphite that can be used to build the Steele interaction potential of these gases on graphene. The goal is to find out hybrid and/or DFT methods that are as accurate as the CCSD(T) on benzene and as accurate as the experimental results on graphene. Calculations of the interaction energy curves of N2 and CO2 on benzene and graphene have been carried out using the CCSD(T) method and several double hybrid, hybrid, and DFT methods that consider the dispersion interactions. The energy curves on benzene have been compared to the CCSD(T) and the energy curves on graphene have been compared with the Steele energy curves. The comparisons indicate that double hybrids with dispersion corrections and ωB97 based DFT methods are accurate enough for benzene. For graphene, only the PBE-XDM functional has a good agreement with the Steele energy curves.

Dye adsorption of aluminium- and zirconium-based metal organic frameworks with azobenzene dicarboxylate linkers.

The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al3+ (Al-AZB) and Zr4+ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 °C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m2/g) than the Zr-AZB (1098 m2/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm3/g and 0.35 cm3/g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption.

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation, Thermal Destruction of Surface Functional Groups, and Carbon Activation (the OTA Method).

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.

Effect of Pore Size Distribution and Amination on Adsorption Capacities of Polymeric Adsorbents.

Polymeric adsorbents with different properties were synthesized via suspension polymerization. Equilibrium and kinetics experiments were then performed to verify the adsorption capacities of the resins for molecules of various sizes. The adsorption of small molecules reached equilibrium more quickly than the adsorption of large molecules. Furthermore, the resins with small pores are easy to lower their adsorption capacities for large molecules because of the pore blockage effect. After amination, the specific surface areas of the resins decreased. The average pore diameter decreased when the resin was modified with either primary or tertiary amines, but the pore diameter increased when the resin was modified with secondary amines. The phenol adsorption capacities of the amine-modified resins were reduced because of the decreased specific area. The amine-modified resins could more efficiently adsorb reactive brilliant blue 4 owing to the presence of polar functional groups.

X-ray microtomography analysis of soil pore structure dynamics under wetting and drying cycles.

The soil water retention curve is one of the most important properties used to predict the amount of water available to plants, pore size distribution and hydraulic conductivity, as well as knowledge for drainage and irrigation modeling. Depending on the method of measurement adopted, the water retention curve can involve the application of several wetting and drying (W-D) cycles to a soil sample. The method assumes soil pore structure is constant throughout however most of the time soil structure is dynamic and subjected to change when submitted to continuous W-D. Consequently, the pore size distribution, as well as other soil morphological properties can be affected. With this in mind, high resolution X-ray Computed micro-Tomography was utilized to evaluate changes in the soil pore architecture following W-D cycles during the procedure of the water retention curve evaluation. Two different soil sample volumes were analyzed: ROIW (whole sample) and ROIHC (the region close to the bottom of the sample). The second region was selected due to its proximity to the hydraulic contact of the soil with the water retention curve measurement apparatus. Samples were submitted to the following W-D treatments: 0, 6 and 12 W-D. Results indicated the soil changed its porous architecture after W-D cycles. The image-derived porosity did not show differences after W-D cycles for ROIW; while for ROIHC it increased porosity. The porosity was also lower in ROIHC in comparison to ROIW. Pore connectivity improved after W-D cycles for ROIHC, but not for ROIW. W-D cycles induced more aligned pores for both ROIs as observed by the tortuosity results. Pore shape showed changes mainly for ROIW for the equant and triaxial shaped pores; while pore size was significantly influenced by the W-D cycles. Soil water retention curve measurements showed that W-D cycles can affect water retention evaluation and that the changes in the soil morphological properties can play an important role in it.

Effect of the moisture equilibrium process on the expansion behavior of instant controlled pressure drop (DIC) drying of dried apple cubes.

BACKGROUND: Recently, consumers' demand on high quality dried fruit or vegetable products have increased dramatically. The instant controlled pressure drop (DIC) dried products have attracted consumers' attention due to its unique sensory characteristics. The product quality, especially the appearance quality of the DIC products, is influenced closely by water status and water distribution in the material, which is rarely reported in the literatures. In this study, a comparison system for the apple cubes with or without the moisture equilibrium process (MEP) was established to explain the effect of the MEP on the expansion behavior of the DIC dried apple cube. RESULTS: The results showed that the MEP could induce a more homogenous spatial distribution of water in the semi-dried apple cube after pre-drying. Meanwhile, the MEP treated and DIC dried apple cubes showed better quality in terms of the appearance and texture properties including high porosity (71.77%), large pores (maximum pore size of 1.55 mm), and thin pore walls (pore wall thickness of 0.079 mm). CONCLUSION: The MEP was approved to be a compulsory treatment to achieve the DIC dried apple cubes with good expansion behavior. © 2019 Society of Chemical Industry.

Short-term changes in soil pore size distribution: Impact of land use.

Changes in land use affect the pore size distribution (PSD) of the soil, and hence important soil functions such as gas exchange, water availability and plant growth. The objective of this study was to investigate potentially damaging and restorative soil management practices on soil pore structure. We quantified the rate of change in PSD six years after changes in land use taking advantage of the Highfield land-use change experiment at Rothamsted Research. This experiment includes short-term soil degradation and restoration scenarios established simultaneously within long-term contrasting treatments that had reached steady-state equilibrium. The land-use change scenarios comprised conversion to grassland of previously arable or bare fallow soil, and conversion of grassland to arable and bare fallow soils. In the laboratory, we exposed intact soil cores (100 cm3) to matric potentials ranging from -10 hPa to -1.5 MPa. Based on equivalent soil mass, the plant available water capacity decreased after conversion from grassland, whereas no change was observed after conversion to grassland. Structural void ratio decreased after termination of grassland and introduction of grassland in bare fallow soil, while no change was seen when changing arable to grassland. Consequently, it was faster to degrade than to restore a complex soil structure. The study illustrates that introducing grassland in degraded soil may result in short-term increase in soil density.

Molecularly imprinted polymers synthesized via template immobilization on fumed silica nanoparticles for the enrichment of phosphopeptides.

Phosphorylation is a protein post-translational modification (PTM) that plays an important role in cell signaling, cell differentiation, and metabolism. The hyper phosphorylated forms of certain proteins have been appointed as biomarkers for neurodegenerative diseases, and phosphorylation-related mutations are important for detecting cancer pathways. Due to the low abundance of phosphorylated proteins in biological fluids, sample enrichment is beneficial prior to detection. Thus, a need to find new strategies for enriching phosphopeptides has emerged. Molecularly imprinted polymers (MIPs) are synthetic polymeric materials manufactured to exhibit affinity for a target molecule. In this study, MIPs have been synthesized using a new approach based on the use of fumed silica as sacrificial support acting as solid porogen with the template (phosphotyrosine) immobilized on its surface. Phosphotyrosine MIPs were tested against a mixture of peptides and phosphopeptides by performing micro-solid phase extraction using MIPs (µMISPE) packed in a pipette tip. First, the capability of the materials to preferentially enrich phosphopeptides was evaluated. In a next step, the enrichment of phosphopeptides from a whole-cell lysate of human embryonic kidney (HEK) 293T cells was performed. The eluates were analyzed using MALDI-MS in the first case and with nano-HPLC-ESI-MS/MS in the second case. The results showed that the MIPs provided affinity for phosphopeptides, binding preferentially to multi-site phosphorylated peptides. The MIPs could enrich phosphopeptides in over 10-fold compared with the number of phosphopeptides found in a cell lysate without enrichment.

Effects of cropping systems upon the three-dimensional architecture of soil systems are modulated by texture.

Soil delivers fundamental ecosystem functions via interactions between physical and biological processes mediated by soil structure. The structure of soil is also dynamic and modified by natural factors and management intervention. The aim of this study was to investigate the effects of different cropping systems on soil structure at contrasting spatial scales. Three systems were studied in replicated plot field experiments involving varying degrees of plant-derived inputs to the soil, viz. perennial (grassland), annual (arable), and no-plant control (bare fallow), associated with two contrasting soil textures (clayey and sandy). We hypothesized the presence of plants results in a greater range (diversity) of pore sizes and that perennial cropping systems invoke greater structural heterogeneity. Accordingly, the nature of the pore systems was visualised and quantified in 3D by X-ray Computed Tomography at the mm and µm scale. Plants did not affect the porosity of clay soil at the mm scale, but at the µm scale, annual and perennial plant cover resulted in significantly increased porosity, a wider range of pore sizes and greater connectivity compared to bare fallow soil. However, the opposite occurred in the sandy soil, where plants decreased the porosity and pore connectivity at the mm scale but had no significant structural effect at the µm scale. These data reveal profound effects of different agricultural management systems upon soil structural modification, which are strongly modulated by the extent of plant presence and also contingent on the inherent texture of the soil.

Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite.

Due to their high-porosity, nanoporous structure and pores, aerogel materials possess extremely low thermal conductivity and have broad potential in the thermal insulation field. Silica aerogel materials are widely used because of their low thermal conductivity and high temperature resistance. Pure silica aerogel is very fragile and nearly transparent to the infrared spectrum within 3⁻8 µm. Doping fibers and opacifiers can overcome these drawbacks. In this paper, the influences of opacifier type and content on the thermal conductivity of silica fiber mat-aerogel composite are experimentally studied using the transient plane source method. The thermal insulation performances are compared from 100 to 750 °C at constant pressure in nitrogen atmosphere among pure fiber mat, fiber mat-aerogel, 20% SiC-fiber mat-aerogel, 30% ZrO2-fiber mat-aerogel and 20% SiC + 30% ZrO2-fiber mat-aerogel. Fiber mat-aerogel doped with 20% SiC has the lowest thermal conductivity, 0.0792 W/m·K at 750 °C, which proves that the proper type and moderate content of opacifier dominates the low thermal conductivity. The pore size distribution indicates that the volume fraction of the micropore and mesopore is also the key factor for reducing the thermal conductivity of porous materials.

Numerical Simulation of the Freeze-Thaw Behavior of Mortar Containing Deicing Salt Solution.

This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.

White matter microstructure from nonparametric axon diameter distribution mapping.

We report the development of a double diffusion encoding (DDE) MRI method to estimate and map the axon diameter distribution (ADD) within an imaging volume. A variety of biological processes, ranging from development to disease and trauma, may lead to changes in the ADD in the central and peripheral nervous systems. Unlike previously proposed methods, this ADD experimental design and estimation framework employs a more general, nonparametric approach, without a priori assumptions about the underlying form of the ADD, making it suitable to analyze abnormal tissue. In the current study, this framework was used on an ex vivo ferret spinal cord, while emphasizing the way in which the ADD can be weighted by either the number or the volume of the axons. The different weightings, which result in different spatial contrasts, were considered throughout this work. DDE data were analyzed to derive spatially resolved maps of average axon diameter, ADD variance, and extra-axonal volume fraction, along with a novel sub-micron restricted structures map. The morphological information contained in these maps was then used to segment white matter into distinct domains by using a proposed k-means clustering algorithm with spatial contiguity and left-right symmetry constraints, resulting in identifiable white matter tracks. The method was validated by comparing histological measures to the estimated ADDs using a quantitative similarity metric, resulting in good agreement. With further acquisition acceleration and experimental parameters adjustments, this ADD estimation framework could be first used preclinically, and eventually clinically, enabling a wide range of neuroimaging applications for improved understanding of neurodegenerative pathologies and assessing microstructural changes resulting from trauma.

Model-based estimation of microscopic anisotropy using diffusion MRI: a simulation study.

Non-invasive estimation of cell size and shape is a key challenge in diffusion MRI. This article presents a model-based approach that provides independent estimates of pore size and eccentricity from diffusion MRI data. The technique uses a geometric model of finite cylinders with gamma-distributed radii to represent pores of various sizes and elongations. We consider both macroscopically isotropic substrates and substrates of semi-coherently oriented anisotropic pores and we use Monte Carlo simulations to generate synthetic data. We compare the sensitivity of single and double diffusion encoding (SDE and DDE) sequences to the size distribution and eccentricity, and further analyse different protocols of DDE sequences with parallel and/or perpendicular pairs of gradients. We show that explicitly accounting for size distribution is necessary for accurate microstructural parameter estimates, and a model that assumes a single size yields biased eccentricity values. We also find that SDE sequences support estimates, although DDE sequences with mixed parallel and perpendicular gradients enhance accuracy. In the case of macroscopically anisotropic substrates, this model-based approach can be extended to a rotationally invariant framework to provide features of pore shape (specifically eccentricity) in the presence of size distribution and orientation dispersion.

Immersion Calorimetry: Molecular Packing Effects in Micropores.

Repeated and controlled immersion calorimetry experiments were performed to determine the specific surface area and pore-size distribution (PSD) of a well-characterized, microporous poly(furfuryl alcohol)-based activated carbon. The PSD derived from nitrogen gas adsorption indicated a narrow distribution centered at 0.57±0.05 nm. Immersion into liquids of increasing molecular sizes ranging from 0.33 nm (dichloromethane) to 0.70 nm (α-pinene) showed a decreasing enthalpy of immersion at a critical probe size (0.43-0.48 nm), followed by an increase at 0.48-0.56 nm, and a second decrease at 0.56-0.60 nm. This maximum has not been reported previously. After consideration of possible reasons for this new observation, it is concluded that the effect arises from molecular packing inside the micropores, interpreted in terms of 2D packing. The immersion enthalpy PSD was consistent with that from quenched solid density functional theory (QSDFT) analysis of the nitrogen adsorption isotherm.

Effect of hypercrosslinking conditions on pore size distribution and efficiency of monolithic stationary phases.

Three dihalogenic solvents differing in the length of alkyl chain (1,2-dichloroethane, 1,4-dichlorobutane, and 1,6-dichlorohexane) with three Friedel-Crafts alkylation catalysts varying in reactivity (AlCl3 , FeCl3 , and SnCl4 ) have been used to prepare hypercrosslinked poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) columns. Hydrodynamic characteristics as well as column efficiency and mass transfer resistance were tuned by the combination of swelling solvent and alkylation reaction catalyst in the modification mixture. The column swelled in 1,6-dichlorohexane and hypercrosslinked in the presence of AlCl3 provided the highest column efficiency and enabled fast isocratic separations of small molecules in a RP mode. To uncover factors controlling the efficiency of hypercrosslinked monolithic columns, we have studied pore volume distribution of prepared columns. We found that column efficiency increases with the higher pore volume of pores smaller than 2 nm.