Micropore Surface Area Research Articles

Carbon Aerogel Based Thin Electrodes for Zero‐Gap all Vanadium Redox Flow Batteries – Quantifying the Factors Leading to Optimum Performance

AbstractDirect growth of resorcinol−formaldehyde carbon aerogels (CAGs) on carbon paper electrodes was achieved using a new approach. Materials with variations in density, mesoporosity and microporosity were prepared. Microstructural properties of the resultant thin electrodes are shown to directly influence performance in zero‐gap redox flow battery (RFB). BET analysis shows a total surface area between 643 to 931 m2 g−1. Deposition of only ≈15 wt.% CAG on the carbon electrode leads to a 320‐fold increase in electrochemical surface area. Analysis of the results saw a strong positive correlation of RFB performance with surface area. The best performing electrodes had a good balance between microporous and external surface area, and on the macroscopic scale had sufficiently large pores to allow efficient electrolyte permeation. The poorest performing electrodes which had the highest surface area, also had poor macroscopic porosity leading to large mass transport and solution resistance losses. The best performing electrodes were tested in a zero‐gap setup using polarization curves, showing a 25 % increase in power density at 100 mA cm−2 and a peak power density of 706 mW cm−2 at 1 V using thin electrodes.

Synthesis of a Zn/Fe–N–C electrocatalyst towards efficient oxygen reduction reaction via a facile one-pot method

The high price and unsatisfactory stability of Pt-based catalysts for the sluggish oxygen reduction reaction (ORR) severely limit the development of fuel cells and metal-air batteries. Therefore, developing Pt-free electrocatalysts with excellent activities and stabilities is significant. Herein, an efficient Zn/Fe–N–C electrocatalyst is synthesized via a facile one-pot method. Owing to its curved nanosheet structure, appropriate microporous and mesoporous specific surface areas, abundant defects and high Fe–Nx content, Zn/Fe–N–C exhibits remarkable ORR activity and stability in alkaline electrolyte. Its half-wave potential is 0.843 V, which is 10 mV higher than that of Pt/C. Moreover, Zn/Fe–N–C also manifests satisfactory performance in a practical Zn-air battery. Its maximum output power density is 108.5 mW cm−2, which is equivalent to that of Pt/C. In this work, a simple synthesis method for highly active ORR electrocatalyst is provided, which can be implemented for the future design and synthesis of electrocatalysts used in fuel cells and metal-air batteries.

Hierarchical MFI Zeolite Catalysts: How to Determine Their Textural Properties?-A Comparative Study

It is important to elucidate the role of the surface areas and pore volumes of hierarchical zeolites to understand their behavior as catalysts. Micro-and mesopore surface areas and volumes of the hierarchical MFI (Mobil Five zeolites) were assessed following several methods: (i) N2 adsorption at 77 K using classical and corrected t-plot analyses methods, (ii) pre-adsorption of n-nonane was followed by the study of the N2 adsorption at 77 K, and (iii) non-local-density functional theory (NLDFT) analysis using either the N2 adsorption method at 77 K or the Ar adsorption method at 87 K. In order to assess the viability of each method, a set of hierarchical MFI-type zeolites was prepared by different approaches: alkaline treatment (desilication), synthesis in clear solution (nanocrystals), synthesis in the presence of bifunctional organic surfactant (nanosheets), and micelle-templating assisted alkaline treatment. NLDFT methods could not be used to accurately determine the micro-and mesopore surface areas, as larger surface areas compared to those obtained using the BET equation were obtained. This overestimation is even more pronounced with Ar at 87 K. Results from the classical t-plot analysis performed under conditions of N2 adsorption at 77 K for mechanical mixtures of MFI and MCM-41 revealed the underestimation of the micropore volumes and the overestimation of the mesopore surface areas. Corrections were provided for t-plot analysis. The results obtained using the corrected t-plot method were in good agreement with the results obtained using the NLDFT method in the presence of Ar at 87 K during the calculation of the micro-and mesopore volumes of hierarchical MFI-type zeolites. Micropore and mesopore surface areas calculated by the corrected t-plot method were in good agreement with those calculated using the n-nonane pre-adsorption method for the hierarchical MFI-type zeolites characterized by the presence of large zeolite domains. The NLDFT method, in the presence of Ar, can be used to assess the micro-and mesopore volumes of the hierarchical zeolites at 87 K. However, it cannot be used to determine the surface areas. The corrected t-plot method can be used to efficiently calculate both the volumes and surface areas.

A time- and space-resolved catalyst deactivation study on the conversion of glycerol to aromatics using H-ZSM-5

A time- and space-resolved deactivation study on the conversion of glycerol to aromatics over H-ZSM-5 was performed. For this purpose, glycerol was vaporized/pyrolyzed in a pyrolysis section followed by a catalytic aromatization step. Benchmark performance showed an induction period of ca. 20 min, followed by a rather constant BTX yield of ca. 25.4 ± 2.2C.% for 3–4 h time on stream (TOS). Subsequently, a rapid drop in BTX yield was observed due to catalyst deactivation. Severe coking leads to coverage of catalyst surface area and blockage of micropores, particularly at the entrance of the catalyst bed at short TOS, indicating the presence of an axial coke gradient in the fixed bed reactor. At longer TOS, coke was formed throughout the bed and negligible BTX yield was shown to be associated with the presence of coke at all bed positions. Besides coking, the acidity of the catalyst was also reduced, and dealumination occurred, both with a similar time–space evolution. The results were explained by a conversion-zone migration model, which includes a deactivation zone (with severely coked catalyst), a conversion zone (BTX formation), and an induction zone (a.o. (de-)alkylation reactions), and describes the time- and space-resolved evolution of coking and relevant changes in other catalyst characteristics.

Electrocatalytic oxygen reduction of COF-derived porous Fe-Nx nanoclusters/carbon catalyst and application for high performance Zn-air battery

The development of non-previous-metal electrocatalyst with low cost, high activity and stability towards oxygen reduction reaction (ORR) remains a challenge. Covalent organic frameworks (COFs) have emerged as promising candidates for the preparation of porous metal/nitrogen co-doped carbon catalysts. In the present work, porous Fe-Nx nanoclusters/carbon catalysts are prepared by pyrolyzing iron-containing covalent-triazine organic frameworks. It is found that the synthesis conditions including pyrolysis temperature and pressure have great impacts on the surface area of micropores, mesopores and macropores, which in turn influences the ORR activity of catalysts by varying the mass diffusion and the contact of active centers with electrolytes. The optimized catalyst (denoted as Fe1.2NC-0.02-800), having the highest both BET and external surface areas, shows much higher kinetic current density and catalytic stability than commercial Pt/C catalyst in ORR process. When being assembled into Zn-air battery, it also exhibits excellent performances in terms of open circuit voltage (1.45 V), power density (210 mW cm−2 at 330 mA cm−2) and specific capacity (713.1 mA h gZn−1), which outperform the corresponding values of Pt/C-based Zn-air battery. Moreover, 15 light-emitting diodes can be powered by two series-connected Zn-air batteries with Fe1.2NC-0.02-800 as the air-cathode catalyst, implying its promising application in clean energy conversion field.

The breakthrough pressure and sealing property of Lower Paleozoic carbonate rocks in the Gucheng area of the Tarim Basin

Deep carbonate reservoirs with great resource potential are key areas for future hydrocarbon exploration with the continuous innovation of deep hydrocarbon accumulation theory and technology. Breakthrough pressure (BP) is the most important parameter used to indicate rock sealing. In this study, X-ray diffraction, CO2 adsorption, N2 adsorption, high-pressure mercury injection, thin section analysis, effective porosity-permeability and BP experiments are conducted to research pore-throat characteristic of carbonate rock and the influencing factor of BP. Pore volume increases with the specific surface area (SSA) of micropore, and has a weak negative and positive correlation with the SSA of mesopore and macropore, respectively. The BP increases with an increase in the micropore proportion and decreases with an increase in the macropore proportion. Compared with R50 (the pore-throat radii corresponding to these mercury saturation of 50%), R35 (the pore-throat radii corresponding to these mercury saturation of 35%) has a better correlation with porosity and permeability and can better characterize the influence of pore throats on the sealing performance of carbonate rock. A low clay content perhaps leads to an inapparent interrelation between clay content and BP. Because of high brittleness of quartz, an increase in quartz content will cause an increase of porosity and permeability, and a decrease in BP. The BP decreases with the increase in effective porosity and permeability, and linear correlations exist among the reciprocal of porosity (A), the −0.407 power of permeability (B), and the BP. The BP calculation formula is fitted based on A and B by the principal component regression (PCR) method of SAS software for carbonate rock in the Ordovician of the Gucheng area.

Facilitating the acidic oxygen reduction of Fe-N-C catalysts by fluorine-doping.

As the alternatives to expensive Pt-based materials for the oxygen reduction reaction (ORR), iron/nitrogen co-doped carbon catalysts (FeNC) with dense FeNx active sites are promising candidates to promote the commercialization of proton exchange membrane fuel cells. Herein, we report a synthetic approach using perfluorotetradecanoic acid (PFTA)-modified metal-organic frameworks as precursors for the synthesis of fluorine-doped FeNC (F-FeNC) with improved ORR performance. The utilization of PFTA surfactants causes profound changes of the catalyst structure including F-doping into graphitic carbon, increased micropore surface area and Brunauer-Emmett-Teller (BET) surface area (up to 1085 m2 g-1), as well as dense FeNx sites. The F-FeNC catalyst exhibits an improved ORR activity with a high E1/2 of 0.83 V (VS. RHE) compared to the pristine FeNC material (E1/2 = 0.80 V). A fast decay occurs in the first 10 000 potential cycles for the F-FeNC catalyst, but high durability is still maintained up to another 50 000 cycles. Density functional theory calculations reveal that the strongly withdrawing fluorine atoms doped on the graphitic carbon can optimize the electronic structure of the FeNx active center and decrease the adsorption energy of ORR intermediates.

Pore evolution model and diagenetic evolution sequence of the Mesoproterozoic Xiamaling shale in Zhangjiakou, Hebei

Current research on diagenesis and its evolution focuses mainly on sandstone reservoirs. Conventional oil and gas reservoir observation techniques for characterizing shale reservoirs are limited, and comprehensive research on nanoscale pore variations, diagenesis and evolution of shale reservoirs, especially immature and low-maturity marine shale reservoirs, is relatively scarce. To reveal the diagenesis and evolution of low-maturity marine shale, geochemical and mineral analyses, quantitative characterization of the pore structure and qualitative characterization of the pore morphology were performed on the Xiamaling shale. With the burial and geothermal history, the Xiamaling diagenetic evolution sequence and the nanoscale pore system evolution were studied. The results show that smectite continually transforms to an illite-smectite (I/S) mixed layer and then quickly transforms to illite and chlorite; the kaolinite content gradually decreases as maturity increases. The hydrocarbon expulsion threshold of the Xiamaling shale is EqRo = 1.0%, and the porosity decreases to a minimum value of EqRo = 1.0% and then increases. The pore structure evolution model shows that the pore volumes (PVs) of micropores and macropores decrease to minima at approximately EqRo = 0.92% and 0.85%, respectively, and then increase; the mesopore PVs continuously decrease. Micropore and mesopore surface areas (SAs) decrease to their minima at approximately EqRo = 0.85% and 1.0%, respectively, and then increase; simultaneously, the macropore SAs continuously decrease. The main diagenetic types of the Xiamaling shale are compaction, dissolution, cementation, thermal maturation of organic matter (OM), and clay mineral transformation; it reaches period B of the middle diagenetic stage, and the diagenetic evolution sequence is determined. The pore system composition and variation characteristics of the Xiamaling shale are analysed, and a corresponding evolution model is established.

Review and new data on the surface properties of palygorskite: A comparative study

Palygorskite is a mineral used in a wide number of industrial sectors. Currently, there are hundreds of studies in which palygorskite is a part of different nanocomposites and bionanocomposites. The surface properties are essential for these applications, and in this work, an in-depth revision of these properties is done, showing that the high variability found cannot be explained only by the number of impurities or by differences in the analysis conditions. To further deepen the knowledge of the surface properties of palygorskite and palygorskitic clays, a comparative study of a wide group of high purity samples is also performed, and new data on these surface properties are provided with the determination of the specific surface area (SSA), micropore surface area (SSAμp), micropore volume (Vμp), external surface area (SSAEx), and mean equivalent pore diameter. Both the bibliographic data and new data show that SSA varies from a few tens of m2g−1 to almost 300 m2g−1, and the microporosity and external surface proportions also vary greatly. The experimental data obtained show that 1) ordinary soft vacuum conditions produce structural folding, which limits the accessibility to the inner part of the structural tunnels; 2) microporosity is related to the intra- and inter-fibre microporosity, depending first on the fibre size, because the shorter the fibre, the higher the partial accessibility to the entrance of the channels; 3) the crystal chemistry of the samples also influences the SSA because the Mg-rich terms, which have higher content of sepiolite polysome proportions in their structure as well as wider and more accessible intracrystalline channels than palygorskite polysomes.

An updated study on NO catalytic oxidation over activated carbon: The effect of pore structure and a dual-site mechanism

NO catalytic oxidation (NOCO) to NO2 is widely believed to be a fundamental step in selective catalytic reduction (SCR) over activated carbon (AC). Thus, the enhancement of NOCO over AC is significant. The effect of the pore structure on NOCO is discussed first. A series of microporous AC samples with various microporous surface areas were prepared, in which a strong positive correlation existed between NO conversion and the microporous surface area. With an increase in the microporous surface area, the NO conversion increased from 13.10% for MAC1 to 41.18% for MAC4. Concurrently, a hierarchical AC sample with an approximate hierarchy degree (the ratio of Vmes+mac to Vt) of 50% demonstrated higher NO conversion than microporous AC when the microporous surface areas were similar. HAC2 exhibited the largest NO conversion (51.58%). Therefore, the microporous surface area and degree of hierarchy are key factors that enhance NO conversion. NOCO has been demonstrated to be an O-enriched process. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) results revealed that carbonyl groups were generated during the NOCO process. Density functional theory calculations were then performed. Carbonaceous models with unsaturated C atom, carbonyl, and lactone groups were constructed, and the corresponding NOCO reaction paths were calculated. A dual-site NOCO mechanism was proposed by combining the experimental and calculation results. Two types of active sites existed: unsaturated C atoms and high-spin density C atoms that affected the kinetic and steady-state stages of NOCO, respectively. The total amount of high-spin density C atoms strongly depends on the microporous surface area. The study of NOCO was updated, which contributed to the preparation of highly efficient AC for NOCO.

Chemical Structure Transformations in Kerogen from Longmaxi Shales in Response to Tectonic Stress as Investigated by HRTEM, FTIR, and 13C NMR

Kerogen molecular structure controls the micropore (<2 nm diameter) evolution in shale and exerts a significant impact on shale gas adsorption, desorption, and diffusion. However, the influence of tectonic deformation on kerogen structure and organic micropores needs intensive study. Our study mainly focuses on the transformations in the extracted kerogen structure and organic micropores of Longmaxi shale during tectonic deformation. Vitrinite reflectance measurement (VRM) and Raman spectroscopy (RS) were utilized to determine the maturity of organic matter. Organic pore network attributes of kerogen samples were estimated using CO2 adsorption experiments. High-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), and 13C nuclear magnetic resonance (13C NMR) were utilized to interpret the kerogen molecular structures of these samples. VRM and RS results show that Longmaxi shale has reached the wet gas window. Adsorption analyses of CO2 indicate that kerogen samples in shale with strong deformation have larger micropore volume and surface area (<2 nm). 13C NMR and FTIR results reveal that the tectonic stress may promote the shedding of aliphatic carbon. HRTEM images exhibit that aromatic rings with a size of 3 × 3 account for the largest proportion in all kerogen samples, which indicates that the kerogen samples have reached a high thermal evolution level, consistent with the Raman experiment. For weakly deformed shale samples, 66.5 and 88.8% of the total number of aromatic rings in LZ-1 and LZ-4 kerogen belong to the major direction (within a 45° range). In the most strongly deformed sample, LZ-2, distribution orientations of aromatic fringes are dispersed and primarily concentrated at 15–105°. Such disorientation of nanometer-sized polyaromatic layers in the strongly deformed sample creates a nanopore network in organic matter (OM) that increases the micropore volume and surface area. These findings from integrated approaches can provide a new perspective of adsorbed gas enrichment in the complex tectonic areas.

Machine learning approaches to rediscovery and optimization of hydrogen storage on porous bio-derived carbon

Three Machine learning (ML) models were constructed and tested to model the hydrogen adsorption of activated carbons (ACs). Although many efforts have been accomplished, the details of micro structure-efficiency of ACs still remains uncovered. Data-based modeling contains the crucial properties of ACs’ structural characteristics such as micropore surface area, pore volume, and pore-size distribution are utilized as inputs for hydrogen adsorption. The proposed models demonstrated their high feasibility to predict the hydrogen uptake with the RMSEs ranged from 0.06 to 0.19. Among them, the Support vector machine (SVM) exhibited the highest accuracy for prediction of hydrogen adsorption on ACs. The sensitivity analysis also showed the importance of micropore surface area and pore widening on hydrogen uptake. Subsequently, the effects of microstructure properties on hydrogen storage were optimized, employing the SVM-based genetic algorithm (GA) technique. By using the optimized structural properties obtained from GA, the hydrogen uptake increased by 2.5 wt%. The precise tuning of textural features significantly revealed the importance of microstructural properties in bio-derived ACs for H2 uptake. This can be a helpful guide for fabrication procedures of porous carbons for H2 adsorption applications.

Pore structural characteristics and methane adsorption capacity of transitional shale of different depositional and burial processes: a case study of shale from Taiyuan formation of the Southern North China basin

Pore structural characteristics and methane adsorption capacity are two significant aspects affecting shale gas potential, but the impact of deposition and burial processes on these two aspects is not clear. Hence, the shale samples of Taiyuan Formation deposited continuously and experienced multi-stage tectonic uplift in Fuyang-Bozhou area of Southern North China Basin were collected in this study. Based on the total organic carbon content analysis, mineral composition determination, low-pressure CO2 and N2 adsorption, high-pressure methane adsorption and argon ion polishing-field emission scanning electron microscope observation. The impact of depositional and burial processes variation on shale reservoir physical properties and adsorption performance is studied. The results display that the pore types of shale samples which were continues deposited and experienced multi-stage tectonic uplift have no obvious differences, while the pore volume as well as specific surface area (SSA) of micropores and mesopores of shale samples under multi-stage tectonic uplift are larger significantly. Meanwhile, the roughness of shale pores increases also. The decrease of loading pressure caused by multi-stage tectonic uplift may be the main factor for the pore structure changes of shale sample. Compared with the continuous deposited samples, the shale samples under multi-stage tectonic uplift have stronger methane adsorption capacity, which is relevant to the greater SSA of micropores as well as mesopores. This study provides an example and new revelation for the influence of depositional and burial processes on shale pore structure and methane adsorption capacity.

Effects of Pore Structure of Different Rank Coals on Methane Adsorption Heat

Adsorption thermodynamic characteristics are an important part of the methane adsorption mechanism, and are useful for understanding the energy transmission mechanism of coalbed methane (CBM) migration in coal reservoirs. To study the effect of coal pore characteristics on methane adsorption heat, five different types of rank coals were used for low-pressure nitrogen, low-pressure carbon dioxide, and methane adsorption experiments. Pore structure and adsorption parameters, including maximum adsorption capacity and adsorption heat, were obtained for five coal samples, and their relationships were investigated. The results show that the low-pressure nitrogen adsorption method can measure pores within 1.7–300 nm, while the low-pressure carbon dioxide adsorption method can measure micropores within 0.38–1.14 nm. For the five coal samples, comprehensive pore structure parameters were obtained by combining the results of the low-pressure nitrogen and carbon dioxide adsorption experiments. The comprehensive results show that micropores contribute the most to the specific surface area of anthracite, lean coal, fat coal, and lignite, while mesopores contribute the most to the specific surface area of coking coal. Mesopores contribute the most to the pore volume of the five coal samples. The maximum adsorption capacity has a significant positive correlation with the specific surface area and pore volume of micropores less than 2 nm, indicating that methane is mainly adsorbed on the surface of micropores, and can also fill the micropores. The adsorption heat has a significant positive correlation with the specific surface area and pore volume of micropores within 0.38–0.76 nm, indicating that micropores in this range play a major role in determining the methane adsorption heat.

Heteroatoms-Doped Hierarchical Porous Carbon Materials Based on Biomass-Metal Ternary Complex for Supercapacitor

Engineering large active surface area, fast ion transfer, and wide work voltage are indispensable for using porous carbon as an electrode material for high energy density and high rate capability supercapacitors. Here, a method is proposed to fabricate N/O/P/S heteroatom co-doped hierarchical porous carbon materials via zinc carbonate hydroxide ([ZnCO3]2∙[Zn(OH)2]3) assisted activation of the biomass-based ternary complex. By adjusting the pH of the ternary complex and the mass ratio of [ZnCO3]2∙[Zn(OH)2]3, it is demonstrated that TCPC-7-0.5 with high specific surface area (1360 m2 g−1), appropriate micropore surface area (672 m2 g−1), and micropore volume (0.3 cm3 g−1) possesses excellent electrochemical performance. The unique pore structure accelerates the transport of electrolyte ions and provides more effective active sites for their adsorption. As a result, as an electrode material for supercapacitors, it maintains excellent frequency response at a larger scan rate of 1 V s−1. The working voltage range of the assembled symmetrical supercapacitor TCPC-7-0.5//TCPC-7-0.5 in 6 M KOH electrolyte can be effectively expanded to 1.2 V. Most importantly, it can simultaneously achieve an energy density of 7.01 W h kg−1 at a high-power density of 15 kW kg−1.

Efficient hyperparameter-tuned machine learning approach for estimation of supercapacitor performance attributes

Recent years have witnessed the rise of supercapacitor as effective energy storage device. Specifically, carbon-based electrodes have been experimentally well studied and used in the fabrication of supercapacitors due to their excellent electrochemical properties. Recent publications have reported the use of Machine Learning (ML) techniques to study the correlation between the structural features of electrodes and supercapacitor performance metrics. However, the poor R-squared values (i.e., large deviations from the ideal value of unity) and large RMSE values reported in these works reflect the lack of accurate models’ development. This work reports the development and utilization of highly tuned and efficient ML models using hyperparameter tuning, that give insights into correlation between the structural features of electrodes and supercapacitor performance metrics namely specific capacitance, power density and energy density. Artificial Neural Networks (ANN) and Random Forest (RF) models have been employed to predict the various in-operando performance metrics of carbon-based supercapacitors based on three input features such as mesopore surface area, micropore surface area and scan rate. Experimentally measured values of these parameters used for training and testing these two models have been extracted from a set of research papers reported in literature. The optimization techniques and various tuning methodologies adopted for identifying model hyperparameters are discussed in this paper. The R2 values obtained for prediction of specific capacitance, power density and energy density using RF model are in the range from 0.8612 to 0.9353 respectively, while the RMSE values of the above parameters are 18.651, 0.2732 and 0.5764 for respective input parameters. Similarly, the R2 values obtained for prediction of specific capacitance, power density and energy density using ANN model are in the range from 0.9211 to 0.9644 respectively, while the RMSE values of the above parameters are 18.132, 0.1601 and 0.5764 for respective input parameters. Thus, the highly tuned ANN and RF models depict higher R-squared and lower RMSE values in comparison to those previously reported in literature, thereby demonstrating the importance of hyperparameter tuning and optimization in building accurate and reliable computational models.

Effects of inhibitors on the sequestration of flue gas in goaf and pore structures of coal

Injecting power plant flue gas into goaf for sequestration can not only reduce the emission of CO2, but can also effectively inhibit the spontaneous combustion of coal left in the goaf. To analyze the effect of the chemical environment in the goaf on the sequestration of CO2 in a coal seam, a home-made adsorption experiment device and ASAP 2020 specific surface analyzer were used to study the regularity of CO2 adsorption in coal and the pore structure of coal before and after inhibition. The results indicate that the adsorption capacity of CO2 in coal increased by 14.05%–21.04% after inhibition. The inhibitors can significantly increase the adsorption capacity of CO2 in coal, enhancing the sequestration of flue gas in goaf.The pore volume and specific surface area of micropores in the coal samples after inhibition are larger compared to those in the raw coal, whereas those of mesopores and macropores are smaller, but those of the micropores are 4.3 and 205 times those of mesopores and macropores, respectively. Thus, the total pore volume and specific surface area of coal increased significantly after inhibition, which is the reason for the increase of CO2 adsorption capacity. The inhibitor does not fundamentally change the pore size distribution of coal, most of the pores in coal are in the pore size range of 0.4–0.6, 0.8–0.9, 1.5–75, and 120–170 nm, which greatly contribute to its pore volume and specific surface area. The pores with a pore size of <7.5 nm are the main adsorption pores in coal, and the inhibitors can significantly increase the number of micropores and mesopores with a pore size of <7.5 nm. The fractal dimension of the coal samples was calculated using the FHH model, which indicated that the intrusion of inhibitors can remove the impurities in pores and reduce the surface roughness of coal. Conversely, the macropores in the coal samples after inhibition are broken and new micropores are generated. This study is of great significance for increasing the sequestration capacity of CO2 in goaf.

Pair Distribution Function Analysis and Electrochemical Performance of Mesoporous Carbon Nanomaterials Synthesized Through KOH and ZnCl2 Activation

Mesoporous carbon has been synthesized by activating carbonized biogas slurry residues with ZnCl2 and KOH simultaneously. The carbon to activating agent mass ratios were kept at 1:4, while the ZnCl2 to KOH mass ratio varied from 4:0, 3:1, 2:2, 1:3, to 0:4. The highest BET specific surface area of 361 m2 g-1, micropore surface area of 231 m2 g‒1, mesopore surface area of 125 m2 g‒1, and total pore volume of 0.23 cm3 g‒1 which amounted to 78% mesopore content, were obtained for the sample with 3:1 ZnCl2 to KOH mass ratio. Scanning electron microscope (SEM) images were acquired to determine the surface morphology and energy dispersive X-ray (EDX) was used to determine surface composition of the samples. The short, medium, and long-range orders of the synthesized materials were studied using pair distribution function (PDF) analysis. PDF showed that in addition to the locally ordered carbon and silica phase components, samples activated using combined ZnCl2 and KOH also contained crystalline Zn2SiO4 phase with the willemite structure. Electrochemical studies in three-electrode cell system revealed maximum specific capacitance of 216 F g‒1 exhibited by sample with a ZnCl2: KOH mass ratio of 3:1 at a scan rate of 5 mV s‒1.&#x0D; Keywords: Mesoporous carbon; Pair distribution function, Specific capacitance, supercapacitor&#x0D;

Preparation and characterization of poly(1-trimethylsilyl-1-propyne) cross-linked by aliphatic diamines

The article describes a new method for the preparation of cross-linked poly(1-trimethylsilyl-1-propyne) (PTMSP) using aliphatic diamines. The developed two-stage method includes selective functionalization of the polymer by the bromination reaction of PTMSP and the subsequent use of functional groups in the polymer for cross-linking by the reaction of bromine substitution in the polymer with a diamine. Under the conditions of a polymer solution with added diamines, the effect of the chain length of the diamine, the reaction temperature, and the bromine content in the polymer on the cross-linking efficiency was studied. It was shown that the cross-linking efficiency depends on the length of the diamine chain and on the bromine content in PTMSP. The identification of cross-linked products was carried out on the basis of elemental analysis data, the stability of the reaction product to the solvent (CCl4), in which the starting brominated PTMSP dissolves, and by IR spectroscopy. Cross-linked films of brominated PTMSP resistant to organic solvents were obtained using 1,12-diaminododecane, which showed the highest efficiency in the reaction in solution. The individual gases (H2, N2, O2, CH4, CO2, and n-C4H10) and mixed n-butane/methane permeability of the pure, brominated and cross-linked PTMSP films were measured. The obtained data demonstrated that cross-linking reduces pure gases permeability as well as mixed n-butane and methane permeability of cross-linked PTMSP films in comparison with initial PTMSP. Cross-linked PTMSP film showed that ideal selectivity calculated from pure gas measurements enhanced (for example, ideal selectivity for СO2/N2 increased from 6.2 to 10.1) or stayed nearly constant (ideal selectivity for n-С4H10/CH4 was 3.6–3.9) compared to initial PTMSP. Whereas, in contrast, the mixed n-butane/methane selectivity decreased from 22 (unmodified PTMSP) to 14 (cross-linked PTMSP). The nanoporous structure unmodified, brominated and cross-linked PTMSP films was studied by the method of low-temperature nitrogen sorption. The decrease in gas/vapor permeability correlates with changes in the specific surface area and pore volume in the series: PTMSP - brominated PTMSP – cross-linked PTMSP. The high values of the specific surface area and volume of micropores indicate a highly developed nanoporous structure of the obtained cross-linked polymer, which is promising as a membrane and highly sorbing material.

Clarifying the Effect of Clay Minerals on Methane Adsorption Capacity of Marine Shales in Sichuan Basin, China

The effect of clay minerals on the methane adsorption capacity of shales is a basic issue that needs to be clarified and is of great significance for understanding the adsorption characteristics and mechanisms of shale gas. In this study, a variety of experimental methods, including XRD, LTNA, HPMA experiments, were conducted on 82 marine shale samples from the Wufeng–Longmaxi Formation of 10 evaluation wells in the southern Sichuan Basin of China. The controlling factors of adsorption capacities were determined through a correlation analysis with pore characteristics and mineral composition. In terms of mineral composition, organic matter (OM) is the most key methane adsorbent in marine shale, and clay minerals have little effect on methane adsorption. The ultra-low adsorption capacity of illite and chlorite and the hydrophilicity and water absorption ability of clay minerals are the main reasons for their limited effect on gas adsorption in marine shales. From the perspective of the pore structure, the micropore and mesopore specific surface areas (SSAs) control the methane adsorption capacity of marine shales, which are mainly provided by OM. Clay minerals have no relationship with SSAs, regardless of mesopores or micropores. In the competitive adsorption process of OM and clay minerals, OM has an absolute advantage. Clay minerals become carriers for water absorption, due to their interlayer polarity and water wettability. Based on the analysis of a large number of experimental datasets, this study clarified the key problem of whether clay minerals in marine shales control methane adsorption.