CO2 Adsorption Characteristics Research Articles

Two Different Atomically Dispersed Pt Atoms Supported on Ceria.

Atomically dispersed metals on oxide supports with different distribution positions or coordination environments can dictate the reactivity; they have therefore attracted tremendous attention recently. Nonetheless, the acknowledging and understanding of different single atoms remain challenging due to the reactivity controversy of the supported single atoms and clusters or nanoparticles, particularly on the widely used ceria supports. Herein, by modulating the loading amount of Pt single atoms carefully with strong electrostatic adsorption on conventionally synthesized ceria supports, we obtained two different atomically dispersed Pt atoms with similar Pt-O coordination environments and CO adsorption characteristics. One is anchored on the surface of ceria, and it can migrate and aggregate once activated with reduction-reoxidation treatments. The other may be trapped by the surface defects or vacancies in ceria and would be fixed on the ceria support firmly in isolated states during activation. Despite the similar CO adsorption during the reaction, the former can catalyze CO oxidation in both the status of single atoms and aggregated PtOx clusters. However, the latter is inactive for the reaction and would not be affected by the activation treatment. It cannot involve the CO oxidation, resulting in the waste of supported Pt atoms.

Multilayer Adsorption Characteristics of CO2 in Organic Nanopores with Different Pore Sizes: Molecular Simulation and Ono-Kondo Lattice Model.

Shale contains numerous organic micropores with significant potential for CO2 storage. To precisely evaluate the CO2 storage potential of shale reservoirs, it is essential to accurately quantify the adsorption of CO2 within these pores. This study used Grand Canonical Monte Carlo (GCMC) molecular simulations to analyze the CO2 adsorption behavior in organic micropores of varying sizes. The study clarified the number and width of the CO2 adsorption layers in micropores of various sizes and proposed a method for segmenting the multilayer adsorption structure. Additionally, the classic Ono-Kondo lattice (OK) model was extended to characterize pore-filling adsorption, incorporating solid-gas and gas-gas interactions. Accurate characterization of CO2 multilayer adsorption and precise calculation of CO2 absolute adsorption in micropores were achieved. Results indicate that CO2 exhibits pore-filling adsorption behavior in organic micropores, forming a multilayer adsorption structure governed by the pore size. Following symmetry principles, the adsorption layer structure in organic micropores can be simplified to a maximum of three layers. When only one adsorption layer forms, its width equals the gas-accessible pore size. For two or more layers, the width of the original layer stabilizes as additional layers form. The stable adsorption layer widths, from nearest to farthest from the pore wall, are 0.33, 0.45, and 0.39 nm. The improved OK model accurately describes CO2 excess and absolute adsorption isotherms across different pore sizes and calculates the CO2 density in each adsorption layer, showing high consistency with GCMC simulation results. These findings highlight the importance of understanding the CO2 multilayer adsorption structure for accurately estimating CO2 adsorption in organic micropores.

Multicomponent adsorption mechanism of CO2, SO2, NO, and C7H8 from flue gases on nitrogen-doped biochar: Experimental and computational insights

The comprehensive control of CO2 and gaseous pollutants in coal-fired flue gas is urgent and difficult. As a green low-cost adsorbent, nitrogen-doped biochar has potential application in the control technology of flue gas pollutants. Still, its multi-component adsorption characteristics for flue gas are unclear. In this study, the multi-component adsorption characteristics of CO2, SO2, NO, and C7H8 on nitrogen-doped biochar were explored at different temperatures (25–120 °C), and the competitive mechanism of multi-component adsorption was revealed through continuous adsorption experiments and numerical calculation. The adsorption capacities of CO2, SO2, NO, and C7H8 by nitrogen-doped biochar can reach 38.1, 78.9, 3.1, and 245.2 mg/g, among which CO2, SO2, and C7H8 show strong competitive effects. Their adsorption capacities are decreased by 42 % (CO2), 28 % (SO2), and 27 % (C7H8) respectively compared with the single-component adsorption. This is because there are not only more C7H8 adsorption sites on nitrogen-doped carbon, but also C7H8 can partially occupy the adsorption sites of SO2 and CO2 during multi-component adsorption. Combined with the calculation results of density functional theory, the competitive ability of the three gases can be ranked as follows: C7H8 > SO2 > CO2.

A generalized adsorption model of CO2-CH4 in shale based on the improved Langmuir model

CO2 enhanced shale gas recovery (CO2-ESGR), as one of the most promising carbon capture, utilization and storage (CCUS) technologies, can both improve the shale gas production for clean energy supply and mitigate greenhouse gas emissions for the goal of carbon neutrality. The adsorption characteristics of CO2 and CH4 in shale play a key role in the reserve assessment of shale gas and the implementation of CO2-ESGR. The problem of accurate prediction of the adsorption and competitive adsorption characteristics of CO2 and CH4 in shale is still one of the main challenges for CO2-ESGR. To bridge the gap, this work developed a generalized prediction model for the adsorption properties of CH4, CO2, and their mixed gas in shale by improving the Langmuir model, covering a large range of temperature, pressure, and total organic carbon content (TOC). The mathematical models for the key parameters of the Langmuir model, the saturated adsorption capacity Q0 and Langmuir pressure PL, were built for the single-component gas based on their functional relationship with temperature and TOC, and for the mixed gas based on their relationship with Q0 and PL of the single-component gas and CO2 content. Then an improved Langmuir model for the adsorption properties of CO2-CH4 in shale was established. The accuracy of the improved model was verified with a relative deviation below 5 % in a large range of temperature (303–363 K), pressure (0–15 MPa) and TOC (1.06 %-3.83 %) by comparing the calculated adsorption with the experimental data. This generalized adsorption model not only ensures the prediction accuracy of CO2-CH4 adsorption characteristics in shale but also expands its application convenience in a large range of temperatures, pressures and TOC, providing a certain theoretical basis for CO2-ESGR technology.

Adsorption and sensing properties of Pd-doped Janus HfSSe monolayer for thermal runaway gases in lithium-ion batteries: A DFT study

Detecting thermal runaway gases in lithium-ion batteries (LIBs) is an effective means of identifying early battery failures and is significant in ensuring the safe operation of LIBs. This work investigated the adsorption characteristics of CO2, CO, H2, CH4, C2H2, C2H4, and H2O on intrinsic and Pd-doped HfSSe monolayers using density functional theory (DFT). Our calculations showed that all gases were physically adsorbed on the intrinsic HfSSe monolayer, but the Pd-doped HfSSe monolayer had an enhanced adsorption effect for gas molecules. Additional computations of the band structure, deformation charge density, density of states, and frontier molecular orbitals revealed that the Pd-HfSSe monolayer demonstrated superior CO and C2H4 adsorption and sensing capabilities. The analysis of recovery time revealed that Pd-HfSSe may be used as a gas sensor for identifying C2H4. This study provides a theoretical basis for applying Pd-HfSSe as a gas sensor to detect thermal runaway gases in LIBs.

Mechanistic study of carbon dioxide sequestration technology using molecular simulations to assess the adsorption of methane and carbon dioxide by different functional groups

To investigate the characteristics of CO2 and CH4 adsorption across various functional groups and to clarify their thermodynamic attributes, slit models of functional groups with different pore sizes and moisture contents were constructed using the Materials Studio software program. The analysis focused on the characteristics of CO2 and CH4 adsorption in six distinct models comprising different functional groups. The results showed that the adsorption activities of the six functional groups followed the order –CHO>–COOH>–OH>-O-CH3 > –CH3 > –CH2CH3. The average adsorption heat of the oxygen-containing functional groups exceeded that of the aliphatic groups for both the single- or two-component injections of CO2. As the moisture content increases, the maximum adsorption capacity of CH4 in the slit models with –CH2CH3, −O-CH3, –COOH, and –OH functional groups show a significant decreasing trend when injecting CH4 with two components. The absolute value of the adsorption energy of CO2 and CH4 decreases with increasing pore size. In the slit models with –CHO and –COOH functional groups, multiple peaks appear in the adsorption energy of CO2, indicating a greater number of adsorption sites. For the two-component injection of CO2 and CH4, the entropy of CO2 in each functional group was minimized at a pore size of 1 nm.

Molecular simulation of the effect of water content on CO2, CH4, and N2 adsorption characteristics of coal

The objective of this work was to investigate the sorption behavior of gases, namely CO2, CH4, and N2, by molecules of coal sampled from Linglu mine under different water inclusion rates. To this end, the adsorption, diffusion, adsorption heat, and potential energy distribution characteristics of the gases in the coal pores at different water inclusion rates were analyzed using molecular dynamics and grand canonical ensemble Monte Carlo methods. The results showed that the adsorption relationship of the coal molecules on CO2, CH4, and N2 exhibited a downtrend followed by an uptrend when the water content was increased from 0 to 3.6%. The adsorption amount of CO2 was approximately twice as much as those of CH4 and N2, indicating that the competitive adsorption advantage of CO2 compared with those of CH4 and N2 was unaffected by the water content. The trend in the average heat of adsorption was generally consistent with the trend in the density of coal molecules under different moisture contents. Under the same conditions, the diffusion coefficient within a coal molecule was negatively related to the water content in the system. The layer spacing of the water molecules (2.875 Å) was greater than the liquid–water layer spacing, indicating the formation of a water molecule layer at this point, which inhibited gas adsorption. This study lays a theoretical foundation for further investigating the microscopic mechanism of coal–water interaction.

Competitive Adsorption of Moisture and SO2 for Carbon Dioxide Capture by Zeolites FAU 13X and LTA 5A

Zeolites exhibit significant potential as porous materials for selective carbon dioxide (CO2) capture, leveraging their distinctive adsorption properties. However, the presence of moisture (H2O) and sulfur dioxide (SO2) in flue gas streams can significantly affect the efficiency of CO2 capture. This study investigates the CO2 adsorption characteristics of zeolites FAU 5A and LTA 13X, revealing the competitive adsorption mechanism between H2O(g), SO2, and CO2. The zeolites exhibit CO2 adsorption capacities of 93.19 mg/g and 95.80 mg/g for 5A and 13X, respectively, and demonstrate good regeneration potential. Metal cations correlated positively with CO2 adsorption. H2O(g), SO2, and CO2 exhibit a competitive adsorption relationship, with H2O(g) having the highest adsorption capacity, followed by SO2 and CO2. Additionally, the synergistic effect of SO2 and H2O(g) on CO2 adsorption is elucidated. These findings provide valuable insights into the competitive adsorption behavior of moisture and SO2 for CO2 capture using zeolites LTA 5A and FAU 13X, contributing to the development of more efficient CO2 capture processes and the design of tailored adsorbents for industrial applications.

Adsorption and Diffusion Properties of Gas in Nanopores of Kerogen: Insights from Grand Canonical Monte Carlo and Molecular Dynamics Simulations

Investigating the adsorption and diffusion processes of shale gas within the nanopores of kerogen is essential for comprehending the presence of shale gas in organic matter of shale. In this study, an organic nanoporous structure was constructed based on the unit structure of Longmaxi shale kerogen. Grand canonical Monte Carlo and molecular dynamics simulation methods were employed to explore the adsorption and diffusion mechanisms of pure CH4, CO2, and N2, as well as their binary mixtures with varying mole fractions. The results revealed that the physical adsorption characteristics of CH4, CO2, and N2 gases on kerogen adhered to the Langmuir adsorption law. The quantity of adsorbed gas molecules increased with rising pressure but decreased with increasing temperature. The variation in the heat of adsorption was also analyzed. Under identical temperature and pressure conditions, the adsorption of CH4 increased with higher mole fractions of CH4, whereas it decreased with greater mole fractions of CO2 and N2. Notably, CO2 molecules exhibited a robust interaction with kerogen molecules compared to the adsorption properties of CH4 and N2. Furthermore, the self-diffusion coefficient of gas within kerogen nanopores gradually decreased with increasing pressure or decreasing temperature. The diffusion capacity of gas molecules followed the descending order N2 > CH4 > CO2 under the same pressure and temperature conditions.

Study on the Effect of H2S on the Adsorption of CH4, N2, and CO2 by Anthracite.

In order to study the effect of H2S on gas adsorption in a coal seam, the adsorption characteristics of single-component CO2, CH4, N2, and H2S and multicomponent H2S mixed with CO2, CH4, and N2 by anthracite were simulated by using the Grand Canonical Ensemble Monte Carlo (GCMC) method. The results show that the adsorption capacity of CO2, CH4, N2, and H2S in anthracite decreases with increasing temperature and increases with increasing pressure. The isothermal adsorption curves of CO2, CH4, N2, and H2S and different proportions of H2S/CH4, H2S/N2, and H2S/CO2 are highly consistent with the Langmuir equation, and the R 2 is above 0.99. Under different temperature and pressure conditions, the adsorption capacity of H2S and CO2 is stronger than that of coal for N2 and CH4, and the adsorption capacity difference is about 3 mmol/g. There is competitive adsorption among H2S, CO2, CH4, and N2, and H2S has a superior adsorption property. When H2S and other gases exist at the same time, the adsorption capacities of CH4, N2, and CO2 are reduced by 48-60%, 81-91%, and 51-66%, respectively.

Straw-based biochar prepared from multi-step KOH activation and its structure-effect relationship of CO2 capture under atmospheric/pressurized conditions via experimental analysis and MD/DFT calculations

Porous carbon-based CO2 capture holds great promise. However, the preparation process, pore structure and oxygen/nitrogen functional groups of porous carbon on CO2 adsorption still remain unclear. Herein, we develope straw-based biochar with ultra-high specific surface area(SSA), high micropore ratio and different O/N content by modifying the two-step KOH activation procedure and confirm the KOH activation mechanism, CO2 adsorption characteristics, and the structure-effect relationship of CO2 capture. The KOH activation process is controlled by the activation temperature and is divided into five temperature zones. The pickling treatment enhanced the activation effect of biochar, with a SSA of 3567.33 m2/g and a microporous ratio of 96.05 %. The potassium-containing active components reacts with the defective carbon structure above 800 °C catalyzed by alkali and alkaline earth metals(AAEMs), but reacts with the aliphatic hydrocarbon group after pickling. H-4–9-4-m has a maximum CO2 adsorption capacity of 24.77 mmol/g (25 °C/30 bar), whereas 4–9-2-m has a maximum capacity of 3.46 (25 °C/1 bar) and 5.42 mmol/g (0 °C/1 bar) and outstanding CO2/N2 selectivity (123 at 0.02 bar). The pressurized CO2 adsorption capacity is positively correlated with total pore volume. While under atmospheric pressure, the optimal adsorption site of biochar at 25 °C is ultramicroporous(0.5 nm) and oxygen-containing functional groups, and transforms into ultramicroporous(0.7 nm) and N-5 groups at 0 °C. The simulation results show that 0.5 nm is the pore size of CO2 adsorption from monolayer to bilayer, and both oxygen/nitrogen-containing groups could increase the CO2 adsorption capacity of biochar. This study provides guidance for the preparation of excellent carbon-based CO2 adsorbents according to application scenarios.

Migration characteristics of constant elements in the process of coal dissolution by liquid CO2

The effect of liquid CO2 on coal dissolution plays a key role in improving coal bed methane (CBM) recovery and CO2 geological storage. In order to study the effect of liquid CO2–H2O reaction on the migration of mineral constant elements in coal, three kinds of coal samples (lignite, bituminous coal, and anthracite) with different degrees of metamorphism were selected as the research objects. The one-factor experiments of dissolution of liquid CO2 and water-bearing coal samples were carried out by simulating the temperature and pressure of the stratum. X-ray fluorescence spectroscopy (XRF) was used to test the changes in the relative content of constant elements in coal samples after liquid CO2 injection under different pressure conditions. Scanning electron microscopy (SEM) was utilized to observe the evolution pattern of the surface features of the coal before and after the dissolution of liquid CO2. A quantitative analysis of coal pore development characteristics was conducted based on low-temperature N2 adsorption/desorption experiments, and isothermal adsorption experiments were carried out before and after etching the coal samples to understand the adsorption characteristics of CH4 and CO2 by coal under different pressure conditions. The research results indicated that the migration ability of constant elements in coal showed a trend of first decreasing and then increasing with the increasing degree of coal metamorphism. Among the three selected coal samples, the migration ability of constant elements was found to be strongest in anthracite, followed by lignite and bituminous coal. Most of the element migration in coal was carried out through chemical reactions (hydrolysis, carbonation, redox), while some elements were primarily transported through physical means (such as the low-temperature impact of liquid CO2). The dissolution process expands the original pore space of coal and generates new pores, greatly increasing the coal's capacity for CO2 adsorption. These findings deepen our understanding of mineral dissolution in coal by liquid CO2 and provide important insights for achieving efficient and long-term coalbed CO2 geological storage and enhanced methane recovery techniques.

Theoretical study on the electrocatalytic CO2 reduction mechanisms using carbon-nanotube-supported carbon-based single metal atom catalysts

In this study, five Ni-doped carbon-based single metal atom catalysts supported by carbon nanotubes, which can be used for electrocatalytic CO2 reduction, were constructed. According to their structures, these catalysts include one Ni phthalocyanine (NiPc) molecule, two di- and tri-coordinated Ni-doped carbon nanoribbons, and two di-/tri-coordination Ni-doped graphene, which are denoted as NiPc/CNT, H2(H3)-Ni/CNT, 2(3)-Ni/CNT respectively. We first optimized their structures and studied the adsorption characteristics of CO2 on these catalysts with PBE+D3 method. Additionally, the electronic structure characteristics were then calculated, and the electrocatalytic mechanisms of CO2 reduction to CO, HCOOH, CH3OH and CH4 using these catalysts were studied in detail. It is found that the electrocatalytic activities of these five catalysts for reducing CO2 follow the order of 2-Ni/CNT>3-Ni/CNT>H3-Ni/CNT>H2-Ni/CNT>NiPc/CNT. As can be seen, the di-coordination catalysts perform best, followed by the tri-coordination catalysts, while the four-coordination NiPc-based catalyst performs worst. Moreover, graphene-based materials have stronger catalytic activities than their nanoribbon counterparts. Apart from these facts, these five catalytic materials may exhibit product selectivity at different limiting potentials, and specific reaction products can therefore be synthesized by controlling the potentials. We simultaneously investigated the mechanism of competing hydrogen evolution reactions in the electrocatalytic reduction of CO2 with five catalysts, and in order to inhibit the competing hydrogen evolution reactions and improve the efficiency of CO2 electrocatalytic reduction, the acidity of the solution can be appropriately reduced. We hope that our present work can provide a theoretical foundation for the future design and synthesis of novel carbon-based electrocatalyst for efficient CO2 reduction.

Adsorption Characteristics of CO2/CH4/H2S Mixtures in Calcite Nanopores with the Implications for CO2 Sequestration

Summary Injecting CO2 into reservoirs for storage and enhanced oil recovery (EOR) is a practical and cost-effective strategy for reducing carbon emissions. Commonly, CO2-rich industrial waste gas is used as the CO2 source, whereas contaminants such as H2S may severely impact carbon storage and EOR via competitive adsorption. Hence, the adsorption behavior of CH4, CO2, and H2S in calcite (CaCO3) micropores and the impact of H2S on CO2 sequestration and methane recovery are specifically investigated. The Grand Canonical Monte Carlo (GCMC) simulations were applied to study the adsorption characteristics of pure CO2, CH4, and H2S, and their multicomponent mixtures were also investigated in CaCO3 nanopores to reveal the impact of H2S on CO2 storage. The effects of pressure (0–20 MPa), temperature (293.15–383.15 K), pore width, buried depth, and gas mole fraction on the adsorption behaviors are simulated. Molecular dynamics (MD) simulations were performed to explore the diffusion characteristics of the three gases and their mixes. The amount of adsorbed CH4, CO2, and H2S enhances with rising pressure and declines with rising temperature. The order of adsorption quantity in CaCO3 nanopores is H2S > CO2 > CH4 based on the adsorption isotherm. At 10 MPa and 323.15 K, the interaction energies of CaCO3 with CO2, H2S, and CH4 are −2166.40 kcal/mol, −2076.93 kcal/mol, and −174.57 kcal/mol, respectively, which implies that the order of adsorption strength between the three gases and CaCO3 is CO2 > H2S > CH4. The CH4-CaCO3 and H2S-CaCO3 interaction energies are determined by van der Waals energy, whereas electrostatic energy predominates in the CO2-CaCO3 system. The adsorption loading of CH4 and CO2 are lowered by approximately 59.47% and 24.82% when the mole fraction of H2S is 20% at 323.15 K, reflecting the weakening of CH4 and CO2 adsorption by H2S due to competitive adsorption. The diffusivities of three pure gases in CaCO3 nanopore are listed in the following order: CH4 > H2S ≈ CO2. The presence of H2S in the ternary mixtures will limit diffusion and outflow of the system and each single gas, with CH4 being the gas most affected by H2S. Concerning carbon storage in CaCO3 nanopores, the CO2/CH4 binary mixture is suitable for burial in shallower formations (around 1000 m) to maximize the storage amount, while the CO2/CH4/H2S ternary mixture should be buried as deep as possible to minimize the adverse effects of H2S. The effects of H2S on CO2 sequestration and CH4 recovery in CaCO3 nanopores are clarified, which provides theoretical assistance for CO2 storage and EOR projects in carbonate formation.

Net-zero carbon configuration approach for direct air carbon capture based integrated energy system considering dynamic characteristics of CO2 adsorption and desorption

Direct air carbon capture (DAC) is a promising negative carbon technology to balance unavoidable carbon emissions from distributed sources. Deploying DAC into the integrated renewable energy system provides an effective way to achieve regional carbon neutrality. Developing a reasonable configuration approach for the DAC-based integrated energy system (IES) is the premise to ensure the stable, flexible, economic and net-zero carbon operation. However, DAC system captures CO2 from the air through adsorption and desorption with a much lower respond speed than other energy generation, conversion and storage equipment in the IES. Meanwhile, the CO2 adsorption/desorption rate varies significantly with time, making the energy consumption of DAC does not fully correspond to the amount of CO2 being captured. Conventional steady-state IES configuration methods fail to reflect such characteristics of the DAC, which may lead to non-optimal or even infeasible configurations. To this end, this paper develops a configuration-oriented dynamic model for the DAC process to correctly reflect the energy consumption characteristics under given internal operating conditions and the variations of the CO2 adsorption/desorption rate over time. The DAC model is embedded into the configuration framework of the DAC-based IES, formulating a novel configuration approach that optimizes the investment, operation and maintenance, carbon reduction and renewables utilization performance. The optimal capacity of DAC and the corresponding time periods for adsorption, desorption and shutdown operation in typical scenario are determined, revealing the coordinated manner of DAC system with other devices within the IES. Case studies demonstrate the effectiveness of the proposed configuration approach, which can meet the carbon neutral target with the lowest economic cost. Further comparisons also verify the advantages of flexible operation of the DAC system to achieve better coordination with renewable generations and more efficient CO2 capture.

Two-dimensional Janus X2STe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties.

This investigation delves into the adsorption characteristics of CO, NO, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.

Highly sensitive sensing of CO and HF gases by monolayer CuCl.

Using a first-principles approach, the adsorption characteristics of CO and HF on a CuCl monolayer (ML) are studied with Grimme-scheme DFT-D2 for accurate description of the long-range (van der Waals) interactions. According to our study, CO gas molecules undergo chemisorption and HF gas molecules show a physisorption phenomenon on the CuCl monolayer. The adsorption energy for CO is -1.80 eV, which is quite a large negative value compared to that on other previously studied substrates, like InN (-0.223 eV), phosphorene (0.325 eV), Janus Te2Se (-0.171 eV), graphene (P-graphene, -0.12 eV, B-graphene, -0.14 eV, N-graphene, -0.1 eV) and monolayer ZnS (-0.96 eV), as well as pristine hBN (0.21 eV) and Ti-doped hBN (1.66 eV). Meanwhile, for HF, the adsorption energy value is -0.31 eV (greater than that of Ti-doped hBN, 0.27 eV). For CO, the large value of the diffusion energy barrier (DEB = 1.26 eV) during its movement between two optimal sites indicates that clustering can be prevented if many molecules of CO are adsorbed on the CuCl ML. For HF, the value of the DEB (0.082 eV) implies that the adsorption phenomenon may happen quite easily upon the CuCl ML. The transfer of charge according to Bader charge analysis and the variation in the work function depend only on the properties of the elements involved, i.e., their nature, rather than the local binding environment. The work function and band-gap energy variation of the CuCl ML (before and after adsorption) show high sensitivity and selectivity of CO and HF binding with the CuCl monolayer. HF molecules give a more rapid recovery time of 1.09 × 10-7 s compared to that of CO molecules at a room temperature (RT) of 300 K, which indicates that the necessary adsorption and reusability of the CuCl ML for HF can be accomplished effectively at RT. Significant changes in the conductivity are observed due to the CO adsorption at various temperatures, as compared to adsorption of HF, which suggests the possibility of a modification in the conductivity of the CuCl ML.

Mechanistic Insights into CO2 Activation on Pristine, Vacancy-containing and Doped Goldene: A Single-Atom Layer of Gold

Goldene, a one-atom-thick gold sheet, is an emerging graphene-like flat 2-dimensional material. In this study, the geometrical and electronic properties, as well as CO2 adsorption characteristics, of the pristine,...

The Variation Law of CO2 Adsorption / Desorption Energy of Coal under Infrared Action

The adsorption / desorption process of coalbed methane is actually a process of mutual transformation between free state and adsorbed state of gas molecules. Because the molecular movement process is inevitably accompanied by energy changes, it is of great significance to study the energy changes in the process of CO2 adsorption / desorption of coal to study the migration law of coalbed methane. The adsorption and desorption characteristics of CO2 on coal under different infrared powers were studied by using the self-designed infrared isothermal adsorption / desorption simulation tester. The energy calculation theory in the adsorption / desorption process was used to obtain the energy change law in the adsorption / desorption process under the experimental conditions. The results show that the CO2 adsorption / desorption efficiency of coal under the action of power infrared can be explained from the energy point of view, and the free energy of the adsorption and desorption state is affected by the infrared power and pressure, which is consistent with the experimental results of CO2 adsorption / desorption of coal under the action of power infrared. The adsorption characteristic curves of different infrared powers have basically the same change trend, which all meet the cubic polynomial fitting relationship, and the fitting degree is high, R2 is above.

On assessing the carbon capture performance of graphynes with particle swarm optimization.

Tackling climate change is one of the greatest challenges of current times and therefore the development of efficient technologies to limit anthropogenic emissions is of utmost urgency. Recent research towards this goal has alluded to the use of carbon-based solid sorbents for carbon capture. Graphynes (GYs), an interesting class of porous carbon membranes, have recently proven their potential as excellent membranes for gas adsorption and separation. Herein, we explored the CO2 and N2 adsorption characteristics and CO2/N2 selectivities of a class of GYs, namely γ-GY-1, γ-GY-2 and γ-GY-4. We investigated the putative global minimum geometries of adsorbed unary (n = 2-10) and binary (n : m; n, m ∈ [1, 8]) clusters of CO2 and N2 by employing a stochastic global optimization method called particle swarm optimization in conjunction with empirical intermolecular force field formulations. The intervening interactions are modeled using various pairwise potentials, including Lennard-Jones potential, improved Lennard-Jones potential, Buckingham potential and Coulombic potential. The binding energies for both unary and binary clusters are highest for adsorption on γ-GY-1, followed by γ-GY-2. The putative global minimum geometries suggested that N2 molecules preferred binding over the pore centres while CO2 molecules showed higher clustering propensity than any binding site preference. The predicted interaction energies suggested higher selectivity for CO2 over N2 for all the three γ-GYs.