Desired Pore Size Distribution Research Articles

High-rate electrochimcal supercapacitor with attractive energy density assembling from infused-undaria-pinnatifida-based activated carbon

In order to achieve attractive energy density and specific capacitance of electrochemical supercapacitor, multi-heteroatom self-doped carbon is prepared by pyrolyzing the aquatic biomass undaria pinnatifida (UP) filled with magnesium acetate (Mg(CH3COO)2). The pyrolysis product of magnesium oxide (MgO), acting as rigid filling, can shape the pore and help to keep the original pore system. The resultant immersed-undaria-pinnatifida-based activated carbon (IUPAC-700) co-doped with multi-heteroatom shows specific surface area of 1116 m2 g−1, pore volume of 1.63 cm3 g−1 and desired pore size distribution. The electrode basing on it delivers specific capacitance of 579.7 F g−1 at the current density of 0.50 A g−1 and 306.0 F g−1 at 100.0 A g−1 in the electrolyte of 1.0 M H2SO4. It exhibits a high specific capacitance of 488.6 F g−1 in the two-electrode system and provides a significant energy density of 28.7 W kg−1 at the power density of 164.0 W kg−1. It also displays perfect cyclic life after 8000 times charge-discharge at the current density of 5.0 A g−1. The assembled supercapacitor can power the LED lights. The sample IUPAC-700 featured with self-doped multi-heteroatoms is a very competitive electrode material for energy storage device with desired comprehensive performance.

Stochastic Generation of Electrolyzer Catalyst Layers

Developing clean energy technologies, such as polymer electrolyte membrane electrolysis (PEMWE), is essential to mitigate the negative impacts of climate change. However, one persistent barrier to PEMWE uptake is high catalyst costs, which can account for up to 47% of total stack costs [1]. This makes the catalyst a key target for cost savings via material optimization, as the mechanisms linking structure, mass transport, and charge transport remain relatively ambiguous in the literature [2], [3]. Previous studies have explored stochastic material generation and pore network modelling in the porous transport layer (PTL), but such analysis has yet to be performed for the bulk catalyst layer [4].In this study, we introduced a method for replicating the complex pore structure observed in commercially available catalyst materials using stochastic generation techniques. This method creates catalyst structures by using a desired pore size distribution (PSD) as an input, identifying and generating the macro- and microporous regions of the PSD, and then combining the two regions using a custom divider. Statistical analysis (two sample t-test and two sample K-S test) was used to determine the similarity of generated structures to previously imaged commercial catalyst materials. Moreover, pore network modelling techniques were applied to the generated structures to evaluate electrical and mass transport properties. Through these methods, we show that both transport properties and PSD characteristics of generated materials were within experimentally measured ranges, and altering elements of the PSD can result in order of magnitude changes in electrical conductivity, proton conductivity, and through plane permeability.The methodology presented in this work can be used to evaluate transport properties of various catalyst and catalyst-layer designs with novel pore size distributions. The local transport properties obtained can provide estimates for catalyst properties seldom reported in the literature, facilitating the design and informing the fabrication of next generation, ultra low loading catalyst materials.[1] A. Mayyas, M. Ruth, et al., Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, United States (2019).[2] Z. Taie, X. Peng, et al., ACS Appl. Mater. Interfaces, 12, 47, 52701–52712 (2020).[3] J. Lopata, Z. Kang, et al., J. Electrochem. Soc., 167. 064507 (2020).[4] J. K. Lee, C. H. Lee, and A. Bazylak, J. Power Sources, 437, 226910 (2019).

Theoretical performance of multiple size-exclusion chromatography columns connected in series

The fundamental relationships are derived for the retention, peak width, and peak capacity of non-retained polymers eluting from multiple standard size-exclusion chromatography (SEC) columns connected in series. The standard SEC columns may have different dimensions and are packed with particles having distinct average particle diameters (APDs) and average mesopore sizes (AMSs). The performances (peak capacity, local resolution power, and sensitivity) of three standard SEC columns connected in series (called a tri-SEC column) packed with bridged-ethylene-hybrid (BEH) fully porous particles (FPPs) having three different APDs (1.7, 2.5, and 3.5 μm) and AMSs (200, 450, and 900 Å, respectively) are calculated as a function of the applied flow rate and size of polystyrene standards. Irrespective of the APD and AMS, the present investigation assumes isomorphological materials relative to the mesopore space of the three different BEH particles. The advantage of a 15 cm long tri-SEC column over a single reference SEC column (APD=3.5 μm, AMS=900 Å), which generates the same back pressure and separation window as those of the tri-SEC column, is expected at flow rates larger than the optimum flow rate generating the maximum peak capacity. The calculations predict a significant relative increase of the peak capacity (from +25% to +85%), resolution of small molecules (from +75% to +225%), and of the detection limit of intermediate size (from +15% to +70%) and largest polymers (from +25 to +110%). This is explained by 1) the exclusion of the largest polymers from the internal volume of the particles having the smallest mesopores (restricted access media) and 2) the minimum dispersion along the columns packed with the smallest particle sizes in the tri-SEC column. The main benefit of multi-SEC columns is to easily adjust the desired pore size distribution by properly selecting the lengths of each individual SEC column. The user can then control the pore size distribution for any specific separation problem. A potential application is theoretically demonstrated for the fast purification of monoclonal antibodies from metabolites, host cell proteins, aggregated forms, and from virus-like particles.

Fabrication of ultrahigh-molecular-weight polyethylene porous implant for bone application

Abstract Porous implants play a crucial role in allowing ingrowth of host connective tissue and thereby help in keeping the implant in its place. With the aim of mimicking the microstructure of natural extracellular matrix, ultrahigh-molecular-weight polyethylene (UHMWPE) porous samples with a desirable pore size distribution were developed by combining thermally induced phase separation and salt leaching techniques. The porous UHMWPE samples consisted of a nanofibrous UHMWPE matrix with a fibre diameter smaller than 500 nm, highly interconnected, with a controllable pore diameter from nanoscale to 300 µm. Moreover, a porous UHMWPE sample was also developed as a continuous and homogeneous coating onto the UHMWPE dense sample. The dense/porous UHMWPE sample supported human foetal osteoblast 1.19 cell line proliferation and differentiation, indicating the potential of porous UHMWPE with a desirable pore size distribution for bone application. An osseointegration model in the sheep revealed substantial bone formation within the pore layer at 12 weeks via SEM evaluation. Ingrown bone was more closely opposed to the pore wall when compared to the dense UHMWPE control. These results indicate that dense/porous UHMWPE could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic application.

N-doped porous carbon film electrodes for electrochemical capacitor, made by electrospray of sol precursors

Heteroatom doping in carbon structure enhances surface wettability, electrical conductivity, and electron-donor/acceptor properties that in turn, improves the electrochemical performance of carbon electrodes. In this article, in situ grown carbon film electrodes are obtained through electrospray of polymeric sol on carbon paper, followed by curing, and carbonization. The nitrogen functionality in these binder-free carbon film electrodes is successfully incorporated from melamine addition in resorcinol-formaldehyde sol. The film electrode shows a capacitance of 223 mF cm−2 (446 F g−1), and volumetric energy density of 15.2 mWh cm−3 at 1 mA cm−2 in a symmetric cell with 2 M KOH as electrolyte. Furthermore, these electrodes exhibit excellent cyclic stability even after 5000 charge-discharge cycles with almost complete capacitance retention at 5 mA cm−2. The outstanding electrochemical performance of carbon film electrodes are due to the combined effect of following steps: (i) incorporation of nitrogen and oxygen in right amount, (ii) retention of the desired pore size distribution, and fraction of micropores through systematic balancing of resorcinol to melamine ratio in precursor sol, (iii) disintegration of sol by electrospray prior to deposition on carbon paper, that in turn produces a porous three-dimensional interconnected network of nanoparticulate film, and (iv) lyophilization of wet gel layer that retains the pore spaces during solvent removal.

Activated carbon with exceptionally high surface area and tailored nanoporosity obtained from natural anthracite and its use in supercapacitors

We have developed high performance supercapacitor electrodes while demonstrating that using one-step simple industry friendly activation technique, precise control over pore size distribution can be obtained from natural resource. Irrespective of the same staring material, natural anthracite, the obtained samples exhibited two distinctly different pore size distributions exploiting the size differences of the activating agents, which are potassium (KOH) and sodium (NaOH) ions respectively. This precise control over pore sizes enabled us to obtain an unprecedented observation of 136% enhancement of energy density while there is no loss of power density was observed. This unique observation is a result of almost no loss in ion diffusion properties within the electrodes, irrespective of the change of electrolyte to more viscous ionic liquid (Ethyl-Methyl Imidazolium Tetrafluoroborate) from a less viscous aqueous and organic based electrolytes. This size-selective activation enabled us tailoring a highly desirable pore size distribution, a combination of bigger micropores and smaller mesopores. This not only provided very high specific surface area of 2934.60 m2/g with a total pore volume of 1.33 cm3/g, and highest capacitance (198.15 F/g) in aqueous electrolyte, it has also resulted in very high energy density of 82.93 Wh/kg and high power density of ~3487 W/kg.

Synthesis of Meso/Macroporous γ‐Alumina via Aluminum Pellet with Controllable Porosity: Ammonium Bicarbonate Influences through Drying and Calcination Steps

AbstractMesoporous and macroporous γ‐alumina have been synthesized using the economic source of aluminum pellets. To manipulate the porosity and overall porous characteristics, ammonium bicarbonate was incorporated into the gel and studied to determine its influence on the porous structure of the obtained γ‐alumina. The nanostructure of the synthesized γ‐alumina, characterized by the N2 sorption isotherms and FESEM analysis, indicated that the γ‐alumina of desired pore size distribution could be achieved using such economical source of aluminum when ammonium bicarbonate was considered to tailor its porous structure. The formation of macropores in synthesized γ‐alumina was confirmed by the FESEM images and the crystalline structure of the γ‐alumina of optimal porous structure was revealed via X‐ray diffraction pattern. Before and after being calcinated at 500 °C, TG‐DTA and FT‐IR analyses were also conducted to better assess the impact that thermal processes could have on ultimate γ‐alumina porous characteristics. Considering the embedded ammonium bicarbonate expander, a two‐step mechanism was finally proposed to explain the observed porosity developed through heating stages. Different porosity patterns developed through drying and calcination steps were then contributed to the reactions taking place at each, and N2 sorption isotherms, as well as the FESEM images, were used to evaluate the introduced pore forming mechanisms.

Polymeric Hollow Fibers: State of the Art Review of Their Preparation, Characterization and Applications in Different Research Areas

In this article an attempt is made to review critically the papers published recently on polymeric hollow fibers and hollow fiber membranes. Hollow fiber membranes emerged in early nineteen sixties at almost the same time as the announcement of the cellulose acetate reverse osmosis membrane for seawater desalination by Loeb and Sourirajan. Since then, the hollow fiber technology has progressed along with the industrial membrane separation processes. Today, hollow fiber membranes are being used in every sector of the manufacturing industry, including gas and vapor separation, seawater desalination and waste water treatment. The fabrication of a hollow fiber membrane with a desirable pore–size distribution and performance is not an easy task. There are many factors controlling fiber morphology during the phase inversion process and, at present, we are not able to say that we fully understand the phenomena involved in the fabrication of hollow fibers. Nevertheless, there has been a large amount of knowledge accumulated during the past fifteen years, which has been supported by an equally large amount of efforts by many researchers. This paper attempts to summarize those works. The authors could however look into only those reports which have appeared in scientific journals and few patents, and they are fully aware that there must be much more information that has not surfaced to the journal publication. It is also the authors’ intention to show the future direction including the research topics that have been studied only little or not at all.

On the methane adsorption capacity of activated carbons: in search of a correlation with adsorbent properties

AbstractBACKGROUND: There exists now a widely held view that the methane storage capacity on an activated carbon is not related to any of the routinely determined properties of the adsorbent, such as surface area or micropore volume. This has been confirmed and a correlation pursued with other physical and/or chemical properties of both commercially available carbons and those prepared in the laboratory. Textural characteristics (from nitrogen adsorption isotherms at 77 K) considered were BET‐equivalent specific surface area, DR micropore volume and Horvath–Kawazoe micropore size distribution. Chemical properties were evaluated using Fourier transform infrared (FTIR) spectroscopy, thermal programmed decomposition (TPD) and Boehm titrations. Both kinetic and equilibrium methane adsorption experiments were performed at 273 and 298 K and up to 3.5 MPa.RESULTS: Using phosphoric acid to activate peach stones together with additional thermal treatment enabled the production of activated carbons with 137 v/v methane adsorption capacity at 298 K.CONCLUSIONS: The presence of acidic surface functional groups has a detrimental influence on methane uptake, due to the chemical inertness of the adsorbate and/or to pore blockage of the adsorbent. Basic surface functional groups (pyrone), together with a desirable pore size distribution centered at ca 0.8 nm, are thought to be responsible for improved methane adsorption capacity on such activated carbons. Copyright © 2009 Society of Chemical Industry

Study on the Hydrodesulfurization Catalyst of Residual Fuel (Part 4)

The control methods of pore properties of catalyst supports and the manufacturing methods of their desirable pore size distribution for hydrodesulfurization catalyst of residual fuel were studied. Namely, the correlations between pore properties of γ-alunzina and preparation and calcination condition of alumina hydrates, especially boehmite gel, were investigated. From the experimental results, the following were obtained.1) With higher hydrolysis temperature, the crystallites became larger, the specific surface area decreased and the pore volume of the pore having diameter less than 600A increased. When aging period of boehmite gel was prolonged, the degree of crystallinity advanced along with the crystal growth of bayerite and consequently, the specific surface area and the pore volume decreased.2) When the alumina hydrates were washed in water, the pore volume and the specific surface area decreased. When they were washed in alcohol, the pore volume and the specific surface area increased on the contrary.3) As the calcination temperature was raised higher, the specific surface area decreased and, in reverse, the pore volume increased.4) The most important effect on the pore structure of the alumina as catalyst support was the permeation of alcohols into the interstice of crystallites of alumina. Also, selecting the preparation conditions of alumina hydrates adequately, the diameter of crystallites could be changed markedly and, consequently, the pore structure could be controlled.5) When the suitable kind of acid was added to alumina hydrates and they were calcined to make alumina supports, the specific surface area was constant independent of the acid concentration, while the pore volume and the mean pore diameter decreased according to increase of the acid cotcentration.