Gas Adsorption Research Articles

Gas sensing performance regulating of ZIF-8 encapsulated WO3 nanosheets

Reasonably regulating the adsorption properties on the surface of metal oxide semiconductors (MOS) to enhance sensor selectivity remains a challenge, limiting their application in detecting diseases biomarkers in human exhaled gas. To address this, we proposed a metal-organic frameworks (MOFs) encapsulated strategy to provide a gas-selective permeable nano-filtration layer for MOS gas sensors. By adjusting the coating thickness of ZIF-8, we successfully modulate the sensing properties of WO₃ to different potential biomarkers. The optimized WO₃/ZIF-8 composite shows improved selectivity and response to various disease biomarkers compared to WO₃ alone. The unique porous structure of ZIF-8 and the heterojunction of WO3/ZIF-8 synergistically promote the gas adsorption performance. QCM test results confirm that ZIF-8 modification effectively regulates gas adsorption on the WO₃ surface. This study provides a valuable reference for designing exhaled gas sensor arrays for detecting serious diseases.

Diffusive nature of different gases in graphite: Implications for gas separation membrane technology

Graphite membranes have gained attention in membrane technology for gas separation due to their high stiffness, strength, and stability in corrosive and high-temperature environments. Graphite exists naturally in geologic media and can also be prepared by synthetic processes. In- situ hydrogen (H2) production in petroleum reservoirs or H2 storage in depleted gas reservoirs results in contamination with CH4 and CO2. To address the separation challenge at the surface, a sustainable downhole wellbore membrane must be available to separate H2, leaving behind CO2 and other gases to improve operational economics. Currently, there are no studies in the literature on the self-diffusivity of gases (CO2, H2, and CH4) in graphite as a function of pore size. To overcome time constraints in diffusivity experiments, this work utilized mathematical models and molecular simulations to delineate the self-diffusivity of gases in graphite of different pore sizes.To acknowledge subsurface operational conditions during in situ hydrogen production, we considered a temperature of 360 K and a wide pressure spectrum from 2 MPa to 20 MPa. In this study, we explored the diffusive nature of H2, CH4, and CO2 gases in different nanopore-sized graphite using analytical and molecular simulation approaches. We validated the results by presenting unrestricted case density calculations. First, effective diffusivity was calculated using the mean free pore path, followed by gas adsorption at high pressures (10–20 MPa) and a temperature of 350 K. The study utilized theoretical models and molecular dynamics (MD) simulations to determine the self-diffusivity of gases in graphite systems with various structures.

Improvement of the flame retardancy of polyamide 6 by the incorporation of UiO-66 and UiO-66/melamine

The flame retardancy of polyamide 6 (PA6) has been investigated through the incorporation of the metal–organic framework (MOF) UiO-66 and a composite of UiO-66/melamine during the extrusion process. The prepared materials have been characterised by various techniques: XRD, XPS, FTIR, TGA, DSC, SEM, EDX and mechanical properties. Moreover, to examine the efficiency of the flame retardants, the composites have been tested using the UL-94 vertical and, horizontal burning test, as well as the limiting oxygen index (LOI). The UL-94 V-2 standard has been achieved with only a 4 wt% load of either UiO-66 or UiO-66/melamine, compared to pure polyamide, which is not classified. The best results have been achieved with the UiO-66/melamine sample at 7 wt%, which prevents the agglomeration of UiO-66 alone. The highest LOI value was also obtained with this sample, achieving a value of 35.5 %, compared to pure PA6 and with UiO-66, which reached values of 22.4 % and 23.2 %, respectively. A flame suppression mechanism of the UiO-66/melamine composite is proposed, based on the formation of zirconium oxide, gas adsorption by the MOF and release of NH3.

Substantial gas enrichment in shales influenced by volcanism during the Ordovician–Silurian transition

The substantial gas enrichment in shales of the Ordovician–Silurian transition was associated with the development of the most favorable source rock. While organic matter enrichment has been linked to intensive volcanism, it remains a challenge to precisely evaluate the impact of the volcanism on substantial gas enrichment containing the largest gas storage capacity. This study focused on consecutive borehole shale samples from the Wufeng–Longmaxi formations during the Ordovician–Silurian transition in southern China. We conducted a comprehensive analysis, integrating the major geological volcanism with high-resolution analysis, including QEMSCAN, argon-ion SEM, thin-section examination, XRD mineralogy, TOC, Hg concentration, petrophysical properties and nanopore structure analysis (low-pressure CO2/N2 gas adsorption, porosity and permeability). The results link the significant shale gas enrichment in Wufeng–Longmaxi formations to intensive volcanism across the Ordovician–Silurian transition. We identified the most favorable shale intervals in the lower Longmaxi Formation, aligning with the peak period of volcanism. This period showed synchronous spikes in Hg, Hg/TOC, and TOC contents. Shale deposited during this favorable paleoenvironment exhibited the highest values of TOC, porosity, permeability, specific surface area, pore volume, maximum gas adsorption capacity, leading to the largest amount of gas content and substantial gas enrichment. Our work, therefore, provides new insights into identifying the most favorable shale gas resources. This knowledge assists in accurate predictions of the stratigraphic ‘sweet spot’ intervals for large shale gas storage capacity, providing crucial information for engineering explorations and developments in shale formations.

A DFT study of SF6 decomposition products (H2S, SO2, and CS2) adsorption and detection on Pd-ZnO/SnS2 ternary composites

Real-time and accurate detection of SF6 decomposition products is a crucial approach to diagnosing internal faults of gas-insulated switchgear (GIS). However, the limited sensitivity and selectivity of SnS2 gas sensors have hindered their further development and application. This study employs density functional theory to design the optimal Pd-ZnO/SnS2 monolayer structure and investigate its adsorption behavior toward H2S, SO2, and CS2. The findings indicate that Pd atom doping and ZnO nanoparticle incorporation significantly enhance the conductivity of the SnS2 monolayer, reducing the band gap to 0.54 eV and lowering the work function by 5.019 eV. Regarding gas adsorption and sensing, the Pd-ZnO/SnS2 monolayer outperforms intrinsic SnS2 and ZnO/SnS2, showing the order in which SF6 decomposition products are selected is: CS2 > SO2 > H2S. Additionally, the sensitivity and recovery time of Pd-ZnO/SnS2 as a gas sensor were evaluated, confirming its excellent sensing performance for SO2 and CS2 detection. This study provides theoretical insights to advance the application of gas sensors in online insulation equipment monitoring.

Different enhancement of Ni doping on La0.3Sr0.7Fe0.9Ti0.1O3-δ electrodes in symmetrical solid oxide cell

Poor catalytic activity is a significant challenge that needs to be addressed to enable the effective use of perovskite electrodes in symmetrical solid oxide cell (SOC). In this study, high-activity Ni ions were doped into the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi91) perovskite lattice, which endowed the materials with different facilitation effects in different atmospheres. In an oxidizing atmosphere, the introduction of Ni ions enables La0.3Sr0.7Fe0.8Ti0.1Ni0.1O3-δ (LSFTNi811) to exhibit higher conductivity and oxygen vacancy content, which enhances the adsorption and dissociation of gases. When used as symmetrical electrodes in a solid oxide electrolysis cell, the LSFTNi811 symmetric cell presents higher electrolysis performance than LSFTi91 (1.78 A cm−2 vs. 1.57 A cm−2) at 1.5 V and 800 °C. This is the highest level reported for a single-phase perovskite electrode, underlining its excellent catalytic activity. In a reducing atmosphere, although Ni doping weakens the structural stability of the material, a large number of NiFe nanoparticles precipitate the H2 reaction after material decomposition. In this situation, LSFTNi811 achieves better performance than LSFTi91 as a symmetrical electrode for the solid oxide fuel cell both before and after decomposition. Therefore, LSFTNi811 is a promising symmetrical electrode material for SOCs.

Exploring Synthesis Strategies and Interactions between MOFs and Drugs for Controlled Drug Loading and Release, Characterizing Interactions through Advanced Techniques.

This study explores various aspects of Metal-Organic Frameworks (MOFs), focusing on synthesis techniques to adjust pore size and key ligands and metals for crafting carrier MOFs. It investigates MOF-drug interactions, including hydrogen bonding, van der Waals, and electrostatic interactions, along with kinetic studies. The multifaceted applications of MOFs in drug delivery systems are elucidated. The morphology and structure of MOFs are intricately linked to synthesis methodology, impacting attributes like crystallinity, porosity, and surface area. Hydrothermal synthesis yields MOFs with high crystallinity, suitable for catalytic applications, while solvothermal synthesis generates MOFs with increased porosity, ideal for gas and liquid adsorption. Understanding MOF-drug interactions is crucial for optimizing drug delivery, affecting charge capacity, stability, and therapeutic efficacy. Kinetic studies determine drug release rates and uniformity, vital for controlled drug delivery. Overall, comprehending drug-MOF interactions and kinetics is essential for developing effective and controllable drug delivery systems.

Inherent porosity of Zeolitic Imidazolate Framework-62 melt leading to formation of the porous melt-quenched glass

Porous glasses produced through melt-quenching of some selective metal organic frameworks like Zeolitic Imidazolate Framework-62 (ZIF-62) and ZIF-4 belong to the advanced functional materials because of their inherent porosity, ease of processing, high gas adsorption capacity and gas separation selectivity. We have delineated thermal induced modifications in the porosity features (pore size, size-distribution and pore density) of crystalline ZIF-62 from room temperature (RT) to its melt-state (> melting point, Tm) followed by its quenching, back to RT, carrying out the depth sensitive positron annihilation lifetime spectroscopy (PALS) measurements in-situ at varying temperatures (RT−Tm). On heating under vacuum, the pores' size as well as size-distribution of crystalline ZIF-62 increases up to ∼473 K as a consequence of removal of entrapped solvent molecules and nonuniform thermal expansion. At higher temperatures (∼473 −573 K), a reduction in pores’ size and size-distribution is observed due to the loss of long range ordering and volume collapse. On melting, ZIF-62 turns into a porous liquid having ∼1.4 times larger pores compared to its crystalline form. The quenching of this porous melt is fully irreversible, and results in the formation of a porous glass having the pores larger than its crystalline counterpart. The in-situ PALS investigation provides the first experimental evidence of inherent porosity in ZIF-62 melt existing at high temperature that has been predicted before through molecular dynamics simulation of the ZIFs-based melts.

Improving gas separation performance by boron nitride nanotubes

The performance of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) in multiple gas separation systems was systematically compared using molecular simulation methods. Findings reveal that under conditions of 298 K and 2 MPa, BNNTs generally show higher adsorption selectivities than CNTs for CH4/N2, CO2/CH4, and CO2/N2 mixtures. Notably, in the CO2/CH4 system, BNNTs exhibit a selectivity of up to 350 at a radius of 0.48 nm, significantly surpassing the 14 observed for CNTs; in the CO2/N2 system, selectivity can reach as high as 969 for BNNTs, contrasting with the 69 for CNTs. Furthermore, BNNTs achieve saturation adsorption for CF4 at 0.04 MPa with a capacity of 2.7 mmol/g, while CNTs show a higher adsorption capacity for N2, reflecting the superior selective adsorption capability of BNNTs for specific gases. Analysis of nanotubes with different chiral configurations led to the recommendation of (11,11) and (7,7) chiralities as optimal structures for efficient gas separation. Fluctuations in energy contributions from fluid-wall interactions in BNNTs, are closely related to their selectivity fluctuations. The results demonstrate that BNNTs, due to their unique structural characteristics, possess significant potential in the field of gas adsorption and separation, particularly in enhancing the selective adsorption of CO2 and CF4.

An improved two-phase rate transient analysis method for multiple communicating multi-fractured horizontal wells in shale gas reservoirs: Field cases study

The reduction in well spacing for multi-fractured horizontal wells (MFHWs) and the increase in infill drilling exacerbate the risk of fracture communication. This presents substantial challenges for the rate transient analysis of the parent–child well system. This study proposes an improved two-phase straight-line analysis method to evaluate the linear flow parameters of multiple communicating MFHWs in shale gas reservoirs. Considering shale gas adsorption–desorption mechanisms, nonuniform length of fractures, stress-dependent effects, and matrix shrinkage effects, two-phase productivity equation is established within the dynamic drainage area (DDA). Subsequently, we develop a three-well square root of time plot based on DDA correction and propose a rigorous workflow for evaluating linear flow parameters in single-well, two-well, and three-well systems. The straight lines on the parent well's square root of the time plot exhibit varying degrees of jumps, depending on the frequency of fracture communication. After communication, it is necessary to adjust the cumulative production and production time of the parent well to accurately recalculate the average pressure within the drainage area. Numerical simulations are employed to generate a series of cases under different reservoir conditions to validate the accuracy of the proposed model. The results show that the model estimates fracture half-lengths with errors within 8%, meeting the precision requirements for field applications. Additionally, the method exceeds numerical simulations in computational speed. Two field case studies in the WY Basin, China, further illustrate the effectiveness and practicality of the proposed method, providing theoretical support for hydraulic fracturing construction design and development planning.

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.

Adsorption of NH [formula omitted], HCHO and C[formula omitted]H[formula omitted] onto Y-modified MoS[formula omitted] monolayer : A DFT study

The detection of indoor hazardous gases poses significant complexity and challenges. Based on first-principles theoretical calculations, Y-adsorbed MoS2 (Y-MoS2) monolayer is selected to investigate its adsorption, magnetism and sensitivity to NH3, HCHO and C6H6 gas molecules. The presence of Y atom profoundly alters the electronic and magnetic properties of MoS2 while enhancing its gas adsorption capability. The adsorption capacity of Y-MoS2 monolayer for these indoor hazardous gases follows the order: HCHO ¿ C6H6 ¿ NH3. Notably, at temperatures around 500 K, the Y-MoS2 monolayer exhibits potential as a sensor material for NH3 based on an analysis of recovery performance in the adsorption system. Although the Y-MoS2 monolayer is not suitable for gas sensing applications with regards to HCHO and C6H6, it can be effectively employed as a gas cleansing substance. These findings provide valuable insights into detecting indoor hazardous gases and contribute to our understanding of the gas sensing mechanisms exhibited by MoS2 materials.

Molecular simulation of gas entrapment near a nanoscale cavity: The interplay of surface wettability, cavity shape, and gas type

Surface cavities play a crucial role in trapping and stabilizing gases, a phenomenon that can be used to facilitate applications in separation and drying processes. Understanding surface characteristics in relation to fluid-surface interactions is essential for designing interfacial properties that enable effective processes. In this work, we adopt a molecular simulation approach to investigate gas adsorption and entrapment in surface defects (cavities), focusing on the influence of surface wettability, cavity shape, and gas type. For this purpose, two types of silica-based surfaces with different levels of wettability (methylated and hydroxylated, with the former having lower water wettability), two cavity shapes with identical opening width and depth (V-shaped and square-shaped), and two types of gas (carbon dioxide and nitrogen) are considered. Our observations indicate that a stable gas nanobubble forms when a methylated surface combines with a square-shaped cavity, regardless of the gas type. In contrast, for hydroxylated surface, gas type becomes important; in a square-shaped cavity, nitrogen forms a stable nanobubble while CO2 is trapped in a monolayer fashion. The interfacial forces between the gas and surface which affects gas configuration near the surface, along with the gas molecules’ self-interaction manifested by solubility, are key to the different entrapment modes for N2 and CO2. Moreover, the square-shaped cavity exhibits better capability in trapping gas compared to the V-shaped cavity due to its higher surface area and smaller opening-to-interior ratio. The results of our molecular simulations can guide the design of surface features and processing systems to modify gas entrapment modes and stabilize nanoscale gas bubbles without altering thermodynamic conditions or fluid properties.

Carbothermally synthesized, lignin biochar-based, embedded and surface deposited nano zero-valent iron composites: Comparative material characterization, selective gas adsorption and nitroaromatics remediation

Biochar (BC) with nanoscale zero valent iron (nZVI) incorporation offers advantageous materials for water purification. Even though the most common approach for nZVI incorporation is the deposition on the carrier surface, embedding in the support matrix has also been reported. However, the behavior of the embedded material in contaminant removal has not been adequately studied while characteristics and the remediation capabilities of the two materials have not been compared. Present study focuses on preparing and extensively characterizing two materials: nZVI embedded in (Lig-e-nZVI) and surface deposited on (Lig-s-nZVI) lignin BC with subsequent comparative study of remedial action for two nitroaromatics, p-nitroaniline (pNA) and p-nitrophenol (pNP). The synthesis of Lig-e-nZVI and Lig-s-nZVI involved simultaneous and subsequent pyrolysis of lignin and carbothermal reduction of the iron salt, respectively. Lig-e-nZVI showed enhanced porosity. XRD confirmed the formation of Fe0. HR-TEM images proved the core-shell structure of nZVI, and an interlayer spacing of 0.36nm of the shell verified that the Fe0 particles are encapsulated with graphene while an iron carbide inner layer was also observed, thinner in Lig-e-nZVI and thicker in Lig-s-nZVI. Band gap energy of 2.54eV suggested a photocatalytic activity of both materials. Best fitted Sips isotherms showed 23.1 and 13.1mgg-1 capacities for Lig-s-nZVI in pNP and pNA adsorption respectively. Highest stability was portrayed by Lig-e-nZVI over 4 regeneration cycles. The physicochemical features of the developed materials further enable selective gas adsorption. Findings provide new insights into physicochemical characteristics and remedial actions of differently synthesized nZVI-BC composites.

Preparation and performance study of sludge biomass bamboo charcoal

Abstract The purpose of this study is to explore a new low-cost and high-efficiency biochar adsorption material. The residual sludge as solid waste and fresh bamboo with fast growth and high yield were used as raw materials, modified by the KOH chemical activation method, and pyrolyzed in a tubular furnace with nitrogen atmosphere to obtain sludge biomass bamboo charcoal. In the performance test, the H2S gas adsorption experiment in a fixed bed reactor and the heavy metal adsorption experiment in soil were designed. Using different proportions of biochar, the preparation process of biochar was optimized by adjusting the raw material ratio and activation conditions. The results showed that when dealing with H2S gas, the appropriate amount of sludge can improve the adsorption effect, while the increase of bamboo component will reduce the adsorption rate. In the soil Cr(VI) restoration experiment, it was found that the best restoration effect was achieved after adding 10% biochar and applying it for 28 days, and the restoration rate reached 63.5%.

A porous three-dimensional Cu-MOF: Preparation and application in supercapacitors, low temperature hydrogen storage and gas separation

Due to its unique porosity, metal–organic frameworks (MOFs) have great application prospects in the fields of gas adsorption and separation. However, the synthesis of multi-functional MOFs is still a great challenge. Herein, a multi-functional Cu-MOF of {[Cu2(TPTA)(H2O)2]·2DMF·NMP·4H2O}n with a porosity of 62.0 % was designed and synthesized. The H2 adsorption amount of Cu-MOF is about 289.2 cm3 g−1 at 77 K and 1 bar. Meanwhile, the selectivity adsorption of Cu-MOF towards CO2 over CH4 (V:V = 0.5:0.5), CO2/N2 (V:V = 0.5:0.5) and CO2/H2 (V:V = 0.5:0.5) is 95.1, 139.2 and 147.5, respectively, which is 1.5 times higher than the previously reported Cu-MOFs. The Cu-MOF@NF//AC asymmetric supercapacitor demonstrates high specific capacitance (53.4 F g−1) and stability (90.3 % after 2000 cycles). Furthermore, this work presents a novel approach to design multifunctional materials with low temperature hydrogen storage, gas separation and energy storage properties.

Advanced setup for in situ positron annihilation lifetime measurements under variable gas atmospheres and humidity: From cryogenic to high temperatures

We present a newly developed instrument for 22Na-based positron-annihilation lifetime spectroscopy, designed to facilitate the simultaneous control of temperature, gas atmosphere, and humidity in a single experimental system. The spectrometer operates within a temperature range of 50–480 K and pressures from 10−6 mbar to 1.5 bars. It features a novel gas dosing chamber that allows in situ adsorption studies with gases such as but not limited to CO2, N2, Ar, O2, and their mixtures, with precise control over mixing ratios. Additionally, the device supports in situ humidity exposure, allowing for comprehensive studies of sample interactions with both humidity and humid gases. Fully automated, the system provides seamless data acquisition and environmental control, including pressure and temperature regulation. We demonstrate the instrument’s capability to elucidate alterations in the free volume of maltodextrin under humidity exposure. Additionally, we illustrate the instrument’s efficacy through case studies on CPO-27 metal-organic frameworks (MOFs), highlighting its versatility in analyzing adsorption phenomena across diverse gas adsorbates and temperatures. This state-of-the-art spectrometer stands as an indispensable tool for probing the physicochemical attributes of materials under varying conditions, providing pivotal insights into gas adsorption mechanisms and material dynamics.

Microscopic scale influence of functional groups on the displacement behavior of coalbed methane by hot humid flue gas: a molecular simulation study based on the dynamic injection process

Building upon the CO2-ECBM technology (CO2-Enhanced Coaled Methane Recovery Technology), hot flue gas injection for displacing coalbed methane has been proposed to improve methane recovery efficiency and reduce the costs associated with CO2 capture during the displacement process as well as flue gas desulfurization and denitrification at coal-fired power plants. To explore the microscopic mechanisms of displacement and the influence of functional groups, this study used Molecular Dynamics (MD) and Grand Canonical Monte Carlo (GCMC) methods with Materials Studio software to model slit pores grafted with various functional groups for gas adsorption simulations. The adsorption characteristics of eight key functional groups (-C=OCH₃, -COOH, -CH₂OH, Ar-OH, -OCH₃, -C6H6, -CH₃, -CH₂) for hot flue gas and methane were analyzed, focusing on adsorption strengths and underlying mechanisms. Simulations of the dynamic injection of hot flue gas were conducted, monitoring energy changes and methane density distribution to establish the relationship between adsorption strength and the difficulty of coalbed methane (CBM) displacement. The results indicate that in this simulation, the methane displacement efficiency using hot flue gas to displace coalbed methane exceeded 98%, demonstrating significantly better displacement performance compared to the use of pure carbon dioxide or nitrogen. Although both methane and hot flue gas show that greater interaction energy with pores makes displacement more difficult, the underlying causes differ. A comparison of the interaction energies between different functional groups and various gases reveals that oxygen-containing functional groups (-C=OCH3, -COOH, -CH2OH, Ar-OH, -OCH3) are unfavorable for the displacement of coalbed methane by wet hot flue gas, whereas aliphatic hydrocarbons (-CH3, -CH2) facilitate the displacement process.

Matrix Compression and Pore Heterogeneity in the Coal-Measure Shale Reservoirs of the Qinshui Basin: A Multifractal Analysis

The application of high-pressure fluid induces the closure of isolated pores inside the matrix and promotes the generation of new fractures, resulting in a compressive effect on the matrix. To examine the compressibility of coal-measure shale samples, the compression of the coal–shale matrix in the high-pressure stage was analyzed by a low-pressure nitrogen gas adsorption and mercury intrusion porosimetry experiment. The quantitative parameters describing the heterogeneity of the pore-size distribution of coal-measure shale are obtained using multifractal theory. The results indicate that the samples exhibit compressibility values ranging from 0.154 × 10−5 MPa−1 to 4.74 × 10−5 MPa−1 across a pressure range of 12–413 MPa. The presence of pliable clay minerals enhances the matrix compressibility, whereas inflexible brittle minerals exhibit resistance to matrix compression. There is a reduction in local fluctuations of pore volume across different pore sizes, an improvement in the autocorrelation of PSD, and a mitigation of nonuniformity after correction. Singular and dimension spectra have advantages in multifractal characterization. The left and right spectral width parameters of the singular spectrum emphasize the local differences between the high- and low-value pore volume areas, respectively, whereas the dimensional spectrum width is more suitable for reflecting the overall heterogeneity of the PSD.

Theoretical Study of the Adsorption and Sensing Properties of Cr-Doped SnP3 Monolayer for Dissolved Characteristic Gases in Oil

Dissolved gas analysis (DGA) is a vital method for the online detection of transformer operation state. The adsorption performance of a SnP3 monolayer modified by transition metal Cr regarding six characteristic gases (CO, C2H4, C2H2, CH4, H2, C2H6) dissolved in oil was studied. The study reveals the relevant adsorption and gas-sensing response mechanisms through calculations of the adsorption energy, density of states, differential charge density, energy gap, and recovery time. The results display a considerable increase in the adsorption effect of the Cr-SnP3 monolayer on six gases. The CO, C2H2, and C2H4 gases lead to chemical adsorption, and the CH4, H2, and C2H6 gases lead to physical adsorption. Combined with the recovery time, the Cr-SnP3 monolayer has a strong adsorption effect on CO and C2H2 gases at normal temperatures and even high temperatures, and the adsorption is stable. C2H4 gas can be rapidly desorbed from the Cr-SnP3 monolayer at 398 K. Therefore, the Cr-SnP3 monolayer can be expected to serve as a CO and C2H2 gas adsorbent and a resistive gas sensor for C2H4 gas. This research offers a theoretical foundation for the development of the Cr-SnP3 monolayer in gas-sensitive materials.