Gas Adsorption Method Research Articles

Synthesis of heterogeneous nanocomposite catalyst ZrO2@SBA-15 for formic acid production from hemicelluloses

Heterogeneous nanocomposite ZrO2@SBA-15 catalysts containing 10 wt. % of zirconium oxide were synthesized by two methods: co-condensation and incipient wetness impregnation. The silica support and catalysts were characterized by X-ray diffraction, gas adsorption, FTIR-spectroscopy and other physicochemical methods. As a result of zirconia introduction into the silica wall, the mesostructured of SBA-15 is preserved, but the specific surface area and pore Volume are reduced. It was established that during one-stage co-condensation synthesis, the particle fibers shorten and stick together. The catalysts were tested in the process of catalytic hydrolysis-oxidation of hemicelluloses of aspen wood. The optimal formic acid synthesis conditions were determined: 150°С, 3 h. The highest formic acid yield obtained over the catalyst obtained by co-condensation under best reaction conditions was 28.4 wt. %.

In-line porosity and hardness monitoring of tablets by means of optical coherence tomography

In-line monitoring of critical quality attributes (CQAs) during a tableting process is an essential step toward a real-time release strategy. Such CQAs can be the tablet mass, the API content, dissolution, hardness and tensile strength. Since dissolution testing is laborious and time-consuming and cannot be performed in-line, it is desirable to replace dissolution testing with predictive models based on other CQAs that affect the dissolution characteristics, such as the tablet porosity and hardness. Traditionally, porosity is determined offline via gas adsorption methods or other techniques, such as Terahertz spectroscopy or gas in scattering media absorption spectroscopy. Tablet hardness is typically established using a hardness tester. While these destructive tests can readily be performed at-line, they have limited applicability in in-line settings for a high-percentage inspection. Optical coherence tomography (OCT) has recently been proposed as a possible tool for determining quality attributes. This work describes the first application of OCT for the prediction of tablet porosity and hardness. OCT measurements of tablets produced in a ConsiGma 25™ tableting line and a Stylcam 200R compaction simulator in several compaction force settings were performed and correlated with the porosity and hardness. It was demonstrated that OCT can easily be installed in-line and provide real-time information about critical material attributes. These insights confirm the applicability of OCT as a real-time quality control tool and its potential to replace time-consuming and destructive offline measurements.

Types of lithofacies in the Lower Cambrian marine shale of the Northern Guizhou Region and their suitability for shale gas exploration

The lithofacies and thermal maturity of the over-mature Lower Cambrian marine shale in the Northern Guizhou Region, and their impacts on reservoir properties in this shale were analyzed by combining geochemistry, mineralogy, and gas adsorption methods. Ten lithofacies were identified, and the dominant lithofacies in the studied shale are lean-total organic carbon (TOC) argillaceous-rich siliceous shale (LTAS), medium-TOC siliceous shale (MTSS), and rich-TOC siliceous shale (RTSS). Since the gas generation potential of organic matter was weak, meso- and macro-pores were compressed or filled during the thermal evolution stage with a vitrinite reflectance (RO) range of 3.0%–4.0%. The controlling factors for methane adsorption capacity in the shale samples are significantly influenced by TOC content rather than thermal maturity. Among the RTSS, MTSS, and LTAS samples, RTSS exhibits the highest favorability for preserving hydrocarbon gas, followed by MTSS. The shale types in this study play a significant role in determining the properties of shale reservoirs, serving as an effective parameter for evaluating shale gas development potential. The RTSS and MTSS with a RO range of 2.0%–3.0% stand out as the most favorable target shale types for shale gas exploration and development.

Graphene oxide aerogels for adsorptive separation of aromatic hydrocarbons and cycloalkanes

Efficient separation of benzene and cyclohexane has critical importance for production of commodity chemicals, and is one of the most challenging separations in the industry. Physisorption by recyclable, porous solids has a significant potential in substituting energy-intensive azeotropic or extractive distillation methods. Reduced graphene oxide aerogels (rGOAs) are emerging materials holding great promise for connecting unique properties of 2D graphene with ordinary 3D materials. The benzene/cyclohexane separation on rGOAs self-assembled by the chemical reduction with l-ascorbic acid, sodium bisulphite and (for the first time) sodium dithionite was studied by dynamic gas adsorption methods, and the adsorption performance was analysed in relation to aerogels physicochemical properties. The aerogel reduced with sodium dithionite (rGOA_DTN) had the highest reduction degree and specific surface area (461.2 m2g-1), with the highest contribution of mesopores. It was also the sample with the uppermost uptake of benzene and cyclohexane. The binary component adsorption on rGOA_DTN resulted in the selectivity of the adsorption of benzene over cyclohexane of 2.1. Adsorption-desorption studies demonstrated the excellent thermal stability of the adsorbent in the long-run operation. Because the adsorption capacity did not correlate with the mesopores but with macropores surface area, the selectivity of the adsorption was attributed to the different physicochemical structure of aerogels surface. The benzene molecule interacted strongly by specific C-H···π interactions, while the cyclohexane molecule was excluded from the surface of aerogels because of its shape/size. Results demonstrated that rGOAs can be a versatile and flexible platform for adsorptive gas-phase hydrocarbons separation.

Investigating antimicrobial behavior of thymol/Zn encapsulated hierarchically structured zeolite and thymol release kinetics

A new bioactive material was proposed by encapsulating thymol molecules and Zn2+ cations within the post-modified intracrystalline voids of hierarchical zeolite X crystals. To enhance the accessibility of thymol molecules within zeolite X crystals, commercial zeolite samples underwent post-synthesis treatment involving consecutive aqueous KCl, NH4Cl, and Na2H2EDTA solutions. The gas adsorption method utilized the encapsulation of both Zn2+ cation and thymol molecules into the resulting hierarchical zeolite X framework, which demonstrated improved antimicrobial activity. While sole thymol-encapsulated zeolite X exhibited no antimicrobial activity against S. aureus, Zn2+ encapsulated zeolite X (ZnX), thymol encapsulated post-treated zeolite X (HX-thy), and both Zn2+ and thymol encapsulated post-treated zeolite X (ZnHX-thy) displayed zone of inhibition values of 18.7 mm, 25.0 mm, and 37.5 mm, respectively. Adding Zn2+ and creating a hierarchical pore system in the zeolite X framework altered the release profiles. The Higuchi kinetic release model has the highest R2 value to describe the process of thymol release from X-thy, whereas the Elovich release model has the best fitting profile of thymol release kinetics from ZnX-thy, HX-thy, and ZnHX-thy. Results indicate that thymol and Zn2+ containing hierarchical porous materials could be beneficial tools for obtaining enhanced antibacterial activity and stability with reduced degradation and volatility of thymol with extended protection against microbial attack due to the controlled release. These findings highlight an innovative approach to designing sustainable and green materials, utilizing modified porous networks that encapsulate natural antibacterial compounds with environmentally benign metal ions.

Synthesis and OER catalytic activity of quasi zeolitic imidazolate Framework-67 having two and three dimensional morphology

Zeolitic imidazolate framework-67 (ZIF-67), in two and three dimensional (2D/3D) morphologies have been synthesized at room temperature using different solvent media, and annealed at 350 and 920 °C to derive the modified ZIF-67 based catalysts. All the ZIF-67 based catalysts were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy, Thermogravimetric analysis, N2 gas adsorption method, and Positron annihilation lifetime spectroscopy. It has been observed that catalytic activity of the ZIF-67 based catalysts towards oxygen evolution reaction (OER) depends on the morphology and annealing-induced modifications in active sites. Among different morphologies of as-synthesized ZIF-67, 2D ZIF-67 (nanosheet and disc like morphology) exhibits the best electrocatalytic activity in as-synthesized as well as in the annealed form in comparison to 3D ZIF-67 (rhombic dodecahedron) owing to their better electronic properties. All the types of ZIF-67 annealed at 920 °C show the lower Tafel slopes suggesting higher OER rate.

Advantages of dual CO2 & O2 adsorption model for assessment of micropore development in biochar during two-stage gasification

Residual biochar has the potential to replace commercial carbons even in highly specialised applications, presuming further advances in the engineered biochar production. Optimising biomass conversion requires dynamic feedback on the resultant char porosity, but investigation of pore size distribution (PSD) in pyrogenic carbons is challenging due to their extremely ultramicroporous nature. The most common probe molecule used in gas adsorption methods, N2, is often unable to access the narrowest pores, while CO2 can analyse only pores <10 Å.We propose an approachable way to evaluate PSD of ultramicroporous carbons by simultaneously fitting the 2D-NLDFT (two-dimensional non-local density functional theory) kernels to the CO2 and O2 isotherms. Using O2 as the probe molecule allowed collecting isotherms for the ultramicroporous pyrolytic char, for which a negligible adsorption of N2 was observed. For the more activated, gasification chars, reaching equilibrium for N2 adsorption took up to 8 h for some datapoints. O2 adsorption was much faster, resulting in the total runtime more than two times shorter than for the N2 tests.By analysing chars from the semi-pilot scale gasifier, we confirmed the dependence of the char structure on the process parameters, but we also suspect a strong influence of the reactor design.

Development of a handheld integrating sphere snow grain sizer (HISSGraS)

Abstract We developed a Handheld Integrating Sphere Snow Grain Sizer (HISSGraS) for field use to measure the specific surface area (SSA) of snow. In addition to snow samples, HISSGraS can directly measure snow surfaces and snow pit walls. The basic measurement principle is the same as that of the IceCube SSA instrument. The retrieval algorithm for SSA from reflectance employs two conversion equations formulated using spherical and nonspherical grain shape models. We observed SSAs using HISSGraS, IceCube and the gas adsorption method in a snowfield in Hokkaido, Japan. Intercomparison of the results confirmed that with HISSGraS direct measurement, SSA profile observations can be completed in just ~1/10 the time required for measurement of snow samples. Our results also suggest that HISSGraS and IceCube have similar accuracy when the same snow samples are measured using the same grain shape model. However, SSAs of near-surface snow layers measured using the three techniques exhibited some biases, possibly due to rapid snow metamorphism or melting during measurement and some technical issues with optical techniques. When excluding SSA data for the surface layer, which metamorphosed remarkably during measurement, IceCube- and HISSGraS-derived SSAs correlated strongly with those obtained by gas adsorption and HISSGraS accuracy is 21–34%.

Optimization of Ni/ZnZr catalyst for enhanced syngas yield in catalytic pyrolysis of rice straw

To enhance the catalytic performance of nickel-based catalysts and improve their efficiency in biomass pyrolysis, a nickel-based catalyst supported on a ZnZr composite carrier was synthesized using the sol-gel method. The morphological changes of the catalyst before and after the reaction were observed using X-ray diffraction, scanning electron microscopy, nitrogen gas adsorption, temperature-programmed reduction, and other methods to analyze its catalytic performance. A series of experiments were conducted to explore the optimal conditions for the catalyst’s gas production, including carrier material ratios, loading amounts, residence time, and reaction temperature. The bimetallic carrier of Zn and Zr provided a higher specific surface area, allowing the metallic nickel to enter its mesopores. The synergistic effect of the bimetallic system facilitated the catalytic activity of nickel, significantly enhancing gas production. The maximum CO and H2 production were achieved at Zn/Zr = 6/4. The catalyst achieved an optimal gas yield of 507 mL/g at a residence time of 20 min and a reaction temperature of 800 °C, demonstrating strong stability.

Copper loaded carbon aerogel from chitosan-precursor promotes thermal decomposition of ammonium perchlorate for solid propellants

Chitosan (CS) was used as a carrier, in which copper particles were loaded, and CS-Cu carbon aerogel was obtained by freeze-drying and high-temperature carbonization, which was characterized by scanning electron microscopy test, Fourier transform infrared spectroscopy test, X-ray diffraction test, X-ray photoelectron spectroscopy, and gas adsorption method. Results show that CS-Cu carbon aerogel is a 3D porous material, and its 3D porous structure provides more active sites for the copper nanoparticles, effectively preventing the agglomeration phenomenon caused by the large surface energy of copper nanoparticles. The CS-Cu carbon aerogel was introduced into the solid propellant system, and the catalytic performance of the CS-Cu carbon aerogel on ammonium perchlorate (AP) was investigated by differential thermal analysis. The results show that the CS-Cu carbon aerogel has good catalytic performance, the high temperature decomposition peak of AP is reduced by 92.4 K and the activation energy is reduced from 215.9 ± 1.3 kJ/mol to 173.7 ± 1.5 kJ/mol for pure AP.

Change of polymeric gel structure of several foamed plastic insulations deteriorated by moisture

Foamed plastic insulations require long-term performance under sustainable development goals. However, in recent years, it has been reported that foamed plastic insulations installed in high-humidity environments, such as under waterproof sheets on a rooftop, absorb moisture and subsequently increase thermal conductivity.The study aims to estimate both moisture absorption and changes in physical properties of foamed plastic insulations after exposure to high humidity and discuss the moisture-induced deterioration based on the results of several experiments.We observe what changes occur in three types of foamed plastic insulation, phenolic foam, polyurethane foam, and extruded polystyrene foam, in a deterioration condition with moisture. In the first step, we verify that the moisture exists in what form and whether moisture condenses inside or blends with the material after deterioration occurs. Precisely, comparing weight changes before and after high-temperature humidity deterioration with two test results. One is changing a polymeric gel structure of the deteriorated insulation with X-ray CT, and another is the amount of adsorbed water vapor on the surface of each insulation with the gas adsorption method. Results from these studies refer that the deteriorated phenolic foam and moisture are assumingly miscible to transform polymeric gel structure.The second step compares how moisture deterioration affects insulation’s thermal characteristics. We evaluated in our previous study when insulations are exposed to the seasonal humidity cycle to apply typical seasonal fluctuation in Northeast Asian countries, affecting more critical damage than a persistent condition to samples. Therefore, we examine the relationship between thermal characteristics and moisture deterioration effect in humidity fluctuations. Resultantly, the phenolic foam’s polymeric gel structure is changed, and its thermal property is affected by humidity swings.The results provide a part of the moisture deterioration mechanism, miscible behavior between moisture and foamed plastic insulations to change polymeric gel structure, which shifts thermal properties.

Microstructural evolution of saturated normally consolidated kaolinite clay under thermal cycles

This study aims to quantify the microstructural evolution of saturated clay during one thermal cycle. For this purpose, five saturated normally consolidated kaolinite clay triaxial specimens were consolidated under the same conditions. One specimen was subjected to a mechanical consolidation only; while the other four specimens were subjected to different thermal paths: freezing (F), freezing-thawing (FT), freezing-thawing-heating (FTH), and freezing-thawing-heating-cooling (FTHC). After completing the mechanical and thermal stages, thin disks were cut from the bottom of each specimen. The microstructures of these disks were preserved using flash freezing and freeze-drying. The evolutions of the microstructure of the specimens during the thermal cycle was assessed using mercury intrusion porosimetry, gas adsorption methods, and processing of scanning electron microscopy (SEM) images. The results show that (1) freezing increased the modal throat size and the specific surface area (SSA); (2) freezing-thawing decreased both modal throat and pore sizes, while the SSA recovered to its initial value; (3) freezing-thawing-heating reduced the pore and throat sizes and SSA even further; and (4) freezing-thawing-heating-cooling caused permanent reduction in SSA and throat and pore size distributions. Finally, the shape of the pores became more circular after temperature changes, while the number of pores increased during the thermal cycle with the highest number corresponding to the end of heating (i.e., the third stage in the thermal cycle).

Final report of CCQM-K172 on measurement of Specific Adsorption A [mol/kg] of Ar on zeolite at liquid argon temperature (to enable a traceable determination of the Specific Surface Area by following ISO 9277)

Main textThe CCQM-K172 key comparison on measurement of Specific Adsorption A [mol/kg] of Ar on zeolite at liquid argon temperature (to enable a traceable determination of the Specific Surface Area by following ISO 9277) has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of specific adsorption of Ar, BET specific surface area) of microporous substances (zeolites, sorbents, ceramics, catalytic agents, etc) used in advanced technology.In this key comparison, a commercial zeolite was supplied as a sample. Five NMIs/DIs participated in this key comparison. All participants used a gas adsorption method, here argon adsorption at 77.3 K, for analysis according to the international standard ISO 9277.In this key comparison, the degrees of equivalence uncertainties for specific adsorption argon, BET specific surface area were established.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Preparation of high near-infrared reflectance mica/(Ni, Sb)-co-doped rutile yellow composite pigment via mechanochemical pretreatment and sintering

Mica/(Ni, Sb)-co-doped rutile yellow composite pigment with a high near-infrared reflectance was prepared via mechanochemical pretreatment and subsequent sintering. (Ni, Sb)-co-doped rutile yellow pigment was synthesized by a solid-phase method in the presence of sodium fluoride (NaF) as a mineralizer, and mica was peeled by ultrafine grinding. The pigment, mica and mica/pigment composite were characterized by X-ray diffraction, laser diffraction particle size analysis, nitrogen gas adsorption method, scanning electron microscopy, energy dispersive spectroscopy, ultraviolet–visible–near-infrared spectroscopy, CIEL*a*b* color scales, and infrared irradiation image, respectively. The results show that the temperature of synthesizing a pure rutile pigment in solid-phase reaction is reduced by 100°C due to the addition of mineralizer NaF. (Ni, Sb)-co-doped rutile pigment has better color rendering performance and near-infrared (NIR) reflectance. Ultrafine grinding produces the finer flatty mica particles with fresh reflective surfaces, thus improving NIR reflectance of peeled mica. In mica/pigment composite prepared via mechanochemical pretreatment and subsequent sintering, peeled mica has a synergistic effect on (Ni, Sb)-co-doped rutile pigment particles to further scatter near-infrared radiation through the multiple layer reflections, leading to a better heat insulation. The high near-infrared reflectance of composite pigment increases to 97.72%, and the b* value of the pigment synthesized with 1 wt% NaF is 37.77. For the irradiation infrared lamp, the surface temperature of aluminum plate coated with mica/(Ni, Sb)-co-doped rutile yellow composite pigment is 40.1 ± 0.2°C, which is lower than that of aluminum plate uncoated determined by thermal camera and thermocouple. When aluminum plate coated with mica/(Ni, Sb)-co-doped rutile yellow composite pigment is under sunshine, its surface temperature is 38.6 ± 0.2°C. In addition, the mechanism of preparing the composite pigment via mechanochemical pretreatment and subsequent sintering and the multiple structure reflection effect on peeled mica surface coated with (Ni, Sb)-co-doped rutile yellow pigment particles were also discussed.

Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide

The utilisation of fuel cells in everyday life is of critical importance for the introduction of clean energy and departure from carbon-based economy. The oxygen reduction reaction (ORR) rate on the cathode is the key factor for effective polymer electrolyte membrane fuel cells. Therefore, novel cathode catalysts have to be designed to reduce the ORR over voltage. One of the most efficient ways to increase the ORR rate is to use nitrogen doping of carbon materials.1 Such materials are also promising for applications in supercapacitors and other energy storage devices.2 In this work, experimental results based on a nitrogen-doped reduced graphene oxide are presented. The nitrogen-doped reduced graphene oxide has been produced by Sea Further SARL using a biological micro-organisms and non-toxic chemicals.3 The material has been characterised by several physical methods: particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, gas adsorption method, and electrical conductivity measurements. X-ray diffraction data reveal the presence of peaks characteristic to reduced graphene oxide. The specific surface area of the bulk material is around 2.4 m2 g− 1 based on the nitrogen adsorption method. The bulk sample, in powder form, exhibited considerable specific conductance under pressure.Additionally, electrochemical measurements have been conducted in 0.1 M HClO₄ and 0.1 M KOH solutions. The electrochemical stability, capacitive behaviour, and ORR activity of nitrogen-doped reduced graphene oxide have been determined using cyclic voltammetry, rotating disc electrode and electrochemical impedance spectroscopy methods. The material under discussion has a good electrochemical stability within the investigated potential region in both media. The measurement data show that the ORR kinetics in alkaline media is much faster than in acidic media. Surprisingly, this material has a high gravimetric capacitance. Therefore, nitrogen-doped reduced graphene oxide has high potential for energy storage devices and is promising co-catalyst material in fuel cell. Acknowledgements This work was supported by the EU through the European Regional Development Fund under project TK 141 “Advanced materials and high-technology devices for energy recuperation systems” (grant number 2014 2020.4.01.15 0011); and by the Estonian Research Council (grant number PUT PRG 676). References N. Daems, X. Sheng, I.F.J. Vankelecom, and P.P. Pescarmona, J. Mater. Chem. A, 2, 4085 (2014).N.A. Elessawy, J.E. Nady, W. Wazeer, and A.B. Kashyout, Sci. Rep., 9, 1129 (2019).V. Iakimov, International Patent Application No. WO2021/059152, WIPO, April 1st 2021.

An environmentally friendly turnkey method to determine pore volume of powdered catalysts

Determination of intraparticle pore volume of powdered catalysts is of great interest in a large number of applications, such as fluidized catalytic cracking. Established methods, including mercury intrusion porosimetry (MIP) and gas adsorption method can only measure the volume of pores within a limited range of pore diameter. In this paper, a turnkey method to determine the total intraparticle pore volume of powdered catalyst by water adsorption is proposed. The detailed experimental procedure, accuracy, factors influencing the quality of measurement results as well as the scientific basis of this method are discussed. The observed sudden increase of powder cohesion at the titration end point is characterized by storage modulus. The results of the water adsorption method are significantly correlated with the results of the widely accepted methods such as MIP. The relevant ASTM standard (D8393–21) has been granted. Quick, convenient, accurate measurement and environmentally friendly properties are the key industrial incentives of this method.

Multiscale Pore Structure Characteristics and Crack Propagation Behavior of Coal Samples from High Gas Seam.

Investigation on the pore-fracture features and crack propagation behavior of coal is necessary to prevent coal mine disasters. The pore structure features of coal samples taken from high gas seam were obtained by mercury injection porosimetry (MIP) and gas adsorption methods. The process of deformation and failure for coal samples under three-point bending conditions were obtained. The results demonstrate that the adsorption pores with diameter less than 100 nm are the most developed and their surfaces are the roughest (the average surface fractal dimension Ds is 2.933). The surface of micro-cracks is smoother (Ds is 2.481), which is conducive to gas seepage. It may be the explanation for that 14-3# coal seam is a high gas seam, while there was almost no gas outburst accident so far. At the initial stage of crack propagation, the main crack on the coal sample expanded along the direction of the natural cracks. In the process of crack propagation, the surface fractal dimension of the main crack increased, suggesting that the bending degree of the main crack enhanced. The brittle characteristics of coal samples can be reflected by the ratio of the dissipated energy to the accumulated energy.

Cell wall pore structures of bamboo evaluated using gas adsorption methods

Abstract The efficient conversion of bamboo biomass into biofuel and biomaterials as well as other chemical treatments are strongly related to the porosity of its cell wall. The present work characterizes the micropore and mesopore structure in the cell walls of six bamboo species using both CO2 and N2 adsorption methods. For comparison, two plantation wood species were also tested. As a whole, the tested bamboo species showed lower cell wall porosity (2.6%–3.8%) than wood species (4.0%–5.1%), indicating a more compact cell wall structure for bamboo than wood. Furthermore, the cell wall pore structure and porosity were shown to be tissue-specific, taking Moso bamboo (Phyllostachys eduli) for example, the parenchyma cells exhibited higher pore volume and porosity compared to the fibers. The obtained results provided additional explanations for the higher biomass recalcitrance of bamboo and bamboo fibers as compared to wood and parenchyma cells, with respect to cell wall pore structure.

Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide

The physical and electrochemical properties of a novel nitrogen-doped reduced graphene oxide (N-rGO) material were studied. The novel material was synthesized using biological microorganisms and non-toxic chemicals. In addition, the effect of the high shear treatment on material particle size and suspension stability was investigated. The material was characterized by particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and gas adsorption methods. The N-rGO material has low porosity but its specific surface area and total pore volume increased fourfold and tenfold, respectively, due to the high shear treatment. Electrochemical oxygen reduction activity measurements were conducted in 0.1 M HClO₄ and 0.1 M KOH solutions using rotating disc electrode and cyclic voltammetry methods.

The investigation of activated carbon by K2CO3 activation: Micropores- and macropores-dominated structure

In this study, the K2CO3 activation of bamboo was investigated in detail, and the structure and properties of the prepared activated carbons were tested for the feasibility of CO2 capture application and the potential for both ion and bacteria adsorption for use in the field of hazardous wastewater treatment. Activated carbons were produced with different activator ratios, from 0.5 to 6 according to the sample mass ratio. The ratio of H or O to C (H/C or O/C) increased with the increasing amount of K2CO3 added for the activation. The samples had a highly-porous microporous structure, in which the micropore volume was calculated to be 0.6 cm3 g−1 by the DR method of the CO2 adsorption isotherm at 298 K. The BET surface area and total pore volume estimated from the N2 adsorption isotherms at 77 K of the activated materials increased according to the increase of the K2CO3 impregnation ratio to a maximum value of 1802 m2 g−1 and 0.91 cm3 g−1, respectively. Moreover, the K2CO3-activated samples had a specific morphology, that is, macropores which are presumed to be derived from bubbles. The X-ray-CT images showed that the bubble-like structure is not only on the surface but also inside the samples. The results of gas adsorption methods, mercury porosimetry, and SEM showed the co-existence of micropores (<2 nm) and macropores (100–10,000 nm). The results highlighted the unique pore structure, that is, the coexistence of micropores and macropores that would contribute to forming solutions for carbon sequestration in the atmosphere and wastewater treatment.