CO2 Solubility Research Articles

Alkylimidazolium-based ionic liquids with tailored anions and cations for CO2 capture.

A systematic investigation was conducted in the present study to determine how various cations and anions affected the solubility of CO2. To investigate the influence of different cations and anions on the solubility of CO2, twelve ILs were synthesized, characterized, and utilized. These ILs comprised five distinct anions (dioctylsulfosuccinate [DOSS], triflouromethanesulfonate [TFMS], dodecylsulfate [DDS], 3-sulfobezoate [SBA], and benzene sulfonate [BS]), and four distinct cations (1-butyl-3-propanenitrile imidazolium [C2CN Bim], 1-hexyl-3-propanenitrile imidazolium [C2CN Him], 1-octyl-3-propanenitrile imidazolium [C2CN Oim], and 1-decyl-3-propanenitrile imidazolium [C2CN Dim]). The synthesized ILs were characterized using NMR and elemental analysis. Their moisture and halide contents were determined. The gravimetric method (MSB) was employed to determine the solubility of CO2 at various pressures (20, 15, 10, 5, and 1 bar). In addition, the effects of temperature on the solubility of CO2 were investigated. The constant of Henry's law (kH) was also calculated, along with thermodynamic properties including standard enthalpy (H0), entropy (S0), and Gibbs free energy (G0).

Impact of water content on minimum miscibility pressure during CO2 flooding in high water-cut reservoirs

This study focused on the X block stratum oil, specifically addressing the application of CO2 displacement technology in enhancing oil recovery under high water content conditions. It systematically investigates the variation of the minimum miscibility pressure (MMP) between CO2 and formation oil at water contents of 0%, 60%, 70%, 80%, and 90%. The research employed slim-tube model simulation experiments and theoretical analysis to explore the impact of different water contents on the physical properties of formation oil and the changes in the interaction mechanism between CO2 and crude oil. The results indicate that the MMP of CO2 flooding is the lowest at 31.11 MPa in the absence of water, reaching the highest value of 37.94 MPa at 90% water content. The MMP of the CO2-formation oil system shows a significant upward trend with increasing water content in the formation, which is related to the stability of the water film, the solubility of CO2, and the interfacial tension between oil and water. Meanwhile, high water content leads to the expansion of formation oil volume, increased viscosity, and compositional changes, collectively influencing the results. This study provides theoretical support for the field application of CO2 flooding and offers critical references for optimizing the oil displacement process.

Reactive capture and electrochemical conversion of CO2 with ionic liquids and deep eutectic solvents.

Ionic liquids (ILs) and deep eutectic solvents (DESs) have tremendous potential for reactive capture and conversion (RCC) of CO2 due to their wide electrochemical stability window, low volatility, and high CO2 solubility. There is environmental and economic interest in the direct utilization of the captured CO2 using electrified and modular processes that forgo the thermal- or pressure-swing regeneration steps to concentrate CO2, eliminating the need to compress, transport, or store the gas. The conventional electrochemical conversion of CO2 with aqueous electrolytes presents limited CO2 solubility and high energy requirement to achieve industrially relevant products. Additionally, aqueous systems have competitive hydrogen evolution. In the past decade, there has been significant progress toward the design of ILs and DESs, and their composites to separate CO2 from dilute streams. In parallel, but not necessarily in synergy, there have been studies focused on a few select ILs and DESs for electrochemical reduction of CO2, often diluting them with aqueous or non-aqueous solvents. The resulting electrode-electrolyte interfaces present a complex speciation for RCC. In this review, we describe how the ILs and DESs are tuned for RCC and specifically address the CO2 chemisorption and electroreduction mechanisms. Critical bulk and interfacial properties of ILs and DESs are discussed in the context of RCC, and the potential of these electrolytes are presented through a techno-economic evaluation.

Amplified Production and Export of Dissolved Inorganic Carbon During Hot and Wet Subtropical Monsoon

AbstractUnderstanding the origins and processes of riverine dissolved inorganic carbon (DIC) is crucial for predicting the global carbon cycle with projected, more frequent climate extremes yet our knowledge has remained fragmented. Here we ask: How and how much do DIC production and export vary across space (shallow vs. deep, uphill vs. depression) and time (daily, seasonal, and annual)? How do the relative contributions of biogenic (soil respiration) and geogenic (carbonate weathering) sources differ under different temperature and hydrological conditions? We answer these questions using a catchment‐scale reactive transport model constrained by stream flow, stable water isotopes, stream DIC, and carbon isotope data from a headwater karstic catchment in southwest China in a subtropical monsoon climate. Results show climate seasonality regulates the timing of DIC production and export. In hot‐wet seasons, high temperature accelerates soil respiration and carbonate weathering (up to a factor of three) via elevating soil CO2 and carbonate solubility, whereas high discharge enhances export by two orders of magnitude compared to cold‐dry seasons. Carbonate weathering is driven more by soil CO2 than water flow. At the annual scale, 92.9% and 7.1% of DIC was produced in shallow and deep zone, respectively, whereas 64.5% and 35.5% of DIC was exported from shallow and deep zone, respectively. These results highlight the uniqueness of subtropical karst areas as synchronous reactors and transporters of DIC during the hot‐wet monsoon, contrasting the asynchronous production and export in other climate regions. A future hotter and wetter climate with more intensive storms in the region may further intensify DIC production and export, accentuating the potential of subtropical karst regions as global hot spots for carbon cycling.

Practical potential of suspension electrodes for enhanced limiting currents in electrochemical CO2 reduction.

CO2 conversion is an important part of the transition towards clean fuels and chemicals. However, low solubility of CO2 in water and its slow diffusion cause mass transfer limitations in aqueous electrochemical CO2 reduction. This significantly limits the partial current densities towards any desired CO2-reduction product. We propose using flowable suspension electrodes to spread the current over a larger volume and alleviate mass transfer limitations, which could allow high partial current densities for CO2 conversion even in aqueous environments. To identify the requirements for a well-performing suspension electrode, we use a transmission line model to simulate the local electric and ionic current distributions throughout a channel and show that the electrocatalysis is best distributed over the catholyte volume when the electric, ionic and charge transfer resistances are balanced. In addition, we used electrochemical impedance spectroscopy to measure the different resistance contributions and correlated the results with rheology measurements to show that particle size and shape impact the ever-present trade-off between conductivity and flowability. We combine the modelling and experimental results to evaluate which carbon type is most suitable for use in a suspension electrode for CO2 reduction, and predict a good reaction distribution throughout activated carbon and carbon black suspensions. Finally, we tested several suspension electrodes in a CO2 electrolyzer. Even though mass transport limitations should be reduced, the CO partial current densities are capped at 2.8 mA cm-2, which may be due to engineering limitations. We conclude that using suspension electrodes is challenging for sensitive reactions like CO2 reduction, and may be more suitable for use in other electrochemical conversion reactions suffering from mass transfer limitations that are less affected by competing reactions and contaminations.

A review on recent advances of cellulose acetate membranes for gas separation.

This review thoroughly investigates the wide-ranging applications of cellulose-based materials, with a particular focus on their utility in gas separation processes. By focusing on cellulose acetate (CA), the review underscores its cost-effectiveness, robust mechanical attributes, and noteworthy CO2 solubility, positioning it as a frontrunner among polymeric gas separation membranes. The synthesis techniques for CA membranes are meticulously examined, and the discourse extends to polymeric blend membranes, underscoring their distinct advantages in gas separation applications. The exploration of advancements in CA-based mixed matrix membranes, particularly the incorporation of nanomaterials, sheds light on the significant versatility and potential improvements offered by composite materials. Fabrication techniques demonstrate exceptional gas separation performance, with selectivity values reaching up to 70.9 for CO2/CH4 and 84.1 for CO2/N2. CA/PEG (polyethylene glycol) and CA/MOF (metal-organic frameworks) demonstrated exceptional selectivity in composite membranes with favorable permeability, surpassing other composite CA membranes. Their selectivity with good permeability lies well above all the synthesised cellulose. As challenges in experimental scale separation emerge, the review seamlessly transitions to molecular simulations, emphasizing their crucial role in understanding molecular interactions and overcoming scalability issues. The significance of the review lies in addressing environmental concerns, optimizing membrane compositions, understanding molecular interactions, and bridging knowledge gaps, offering guidance for the sustainable evolution of CA-based materials in gas separation technologies.

Highly selective capture of sulfur dioxide by low viscosity 1,2,4-triazole + [Emim]Cl deep eutectic solvents

Sulfur dioxide (SO2) is a toxic gas emitted from industrial waste gases, and its removal is crucial to improve the quality of the atmosphere and reduce the harm to human health. In this work, we investigated the absorption of SO2 by deep eutectic solvents (DESs) with low viscosity 1,2,4-triazole (Trtz) and 1-ethyl-3-methylimidazole chloride ([Emim]Cl) under different conditions. We briefly investigated the mechanism of sulfur dioxide absorption by DESs and measured the absorption performance of Trtz + [Emim]Cl DESs for SO2 at different molar ratios. The experimental results show that all Trtz + [Emim]Cl DESs have good capture performance for SO2, among which 298.2 K Trtz + [Emim]Cl (1:3) DES has an absorption capacity of 18.15 mol/kg (102.2 kPa) for SO2, surpassing most previously reported deep eutectic solvents. We found that the solubility of CO2 and N2 is much lower than that of SO2. The absorption capacity of DESs for SO2 is about 452 times that of CO2 and 1530 times that of N2.Therefore, this absorbent has extensive application prospects in the field of SO2 gas capture.

Low molecular weight carbohydrate patterns of mangrove macroalgae from different climatic niches under ocean acidification, warming and salinity variation

Ocean acidification has increased due to the enhanced solubility of CO2 in seawater. Mangrove macroalgae in tropical and subtropical coastal regions can benefit from the higher availability of CO2 for photosynthesis and primary production. However, they can be negatively affected by the simultaneously occurring warming and increased salinity in estuaries. Thus, we analyzed the isolated effects of ocean acidification and the interactive effects of increased temperature and salinity on the low molecular weight carbohydrate (LMWC) contents of the mangrove red macroalgae Bostrychia montagnei and Bostrychia calliptera from Brazilian tropical and subtropical populations. Specimens from both climatic niches were tolerant to pH decreased by CO2 enrichment and enhanced their LMWC contents under increased availability of CO2. Specimens from both climatic niches also accumulated their dulcitol and sorbitol contents to cope with warming and salt stress. Nevertheless, temperature of 34 °C was lethal for tropical macroalgae, while 29 °C and 31 °C were lethal for subtropical B. calliptera under salinity of 35. Tropical and subtropical B. montagnei synthesized dulcitol (5–110 mmol kg−1 dry weight) and sorbitol (5–100 mmol kg−1 dry weight) as osmoregulatory, energy and thermal protection compounds, whereas tropical and subtropical B. calliptera synthesized mainly dulcitol (10–210 mmol kg−1 dry weight). Although digeneaside has an energy function in Bostrychia spp., it is not an osmolyte or thermal protection compound. Our data demonstrated that both tropical and subtropical Bostrychia spp. benefit from ocean acidification by CO2 enrichment, increasing their LMWC contents. However, warming and increased salinity in estuaries will be detrimental to them, even they producing protective metabolites. Multifactorial approaches are recommended to investigate whether negative effects of increased temperature and salinity nullify positive effects of ocean acidification on these Bostrychia species/populations.

(Invited) High-Rate CO2 Reduction Reactions: From Electrocatalysts to Gas-Diffusion Electrodes

Excessive emissions of carbon dioxide (CO2) from the use of fossil fuels are becoming a serious obstacle to the sustainable development of society. Electrochemical CO2 reduction (CO2RR) into value-added products using solar electricity is a promising technology to close the carbon cycle and sequester anthropogenic CO2 into chemical feedstocks.[1] The practical implementation of CO2RR requires a high current density, as the current density for CO2RR is directly correlated to the capital cost of the electrodes and electrochemical cells. The use of gas diffusion electrodes (GDEs) effectively accelerates CO2RR by overcoming the mass transport limitation due to the inherently low diffusion and solubility of CO2 in water. This presentation summarises our recent studies on high-rate CO2RR from the point of view of both novel electrocatalyst designs and appropriate electrode assembly. Single-atom electrocatalysts (SAECs), consisting of single isolated metal sites dispersed on heterogeneous supports, are one of the promising electrocatalysts for high-rate gaseous CO2RR. We have employed various single metal-doped covalent triazine frameworks (M-CTFs) as a platform for CO2RR electrocatalysts on GDEs and systematically investigated them to derive sophisticated design principles using a combined computational and experimental approach.[2-4] The Ni-CTF exhibited both high selectivity and high reaction rate for CO production. In contrast, the Sn-CTF exhibited selective formic acid production, and the faradaic efficiencies (FEs) and partial current density reached 85% and 150 mA/cm2, respectively.[2] These results were in close agreement with the intermediate CO2RR adsorption strength obtained by DFT calculations. In addition to the synthesis of efficient electrocatalysts, the triple phase boundary (TPB) at the GDE, where the catalyst material, electrolyte, and gas pores intersect, needs to be enlarged for high-rate gaseous CO2RR.[5,6] We successfully increased the partial current density for multicarbon products (C2+) over cupric oxide (CuO) nanoparticles on gas diffusion electrodes in neutral electrolytes to a record value of 1.7 A/cm2 by maximizing the area of the CO2RR active interface.[5] In particular, we demonstrated that the thickness of catalyst layers was one highly sensitive factor in determining the maximum current density for C2+. Although the GDE and electrocatalyst used in this case are not unique, the optimized assembly elicits their undermined potential.[1] K. Kamiya, Nakanishi* et al. Chem. Lett. 2021, 50, 166-179. [2] S. Kato, K. Kamiya* et al. Chem. Sci., 2023, 14, 613–620. [3] P. Su, K. Kamiya*et al. , Chem. Sci., 2018, 9, 3941-3947. [4] K. Kamiya* Chem. Sci. 2020, 11, 8339–8349. [5] A. Inoue, K. Kamiya* et al. EES Catal. 2023, 1, 9-16. [6] T. Liu*, K. Kamiya* et al. Small 2022, 18, 2205323.

Quantitative Analysis of CO2 Evolution in an Alkaline Electrolyte Solution By Differential Electrochemical Mass Spectroscopy

CO2 is involved in various main and side reactions of electrochemical energy devices, such as carbon corrosion reactions and alcohol oxidation reactions. Differential electrochemical mass spectroscopy (DEMS) has been intensively applied in acidic electrolyte solutions to analyze these reactions. DEMS is the in-situ electrochemical measurement technique to analyze volatile species with the mass spectrometer (MS). However, the applications of DEMS to alkaline electrolyte solutions have been limited due to the high solubility of CO2 in alkaline solutions. While "conventional DEMS cells," where porous thin-film working electrodes are formed onto polytetrafluoroethylene (PTFE) membrane interface, can quantitatively analyze CO2 that has not dissolved into the electrolyte yet [1], the working electrode materials are limited to those that can be deposited on porous PTFE membrane as porous thin-films. Recently, Möller et al. have developed the DEMS system, which can detect CO2 from general planer electrodes coated by catalyst powders by combining a neutralizer and "dual thin-layer flow cell" [2]. However, due to the relatively low detection limit, quantitative analysis of evolved CO2 has not been accomplished. In this study, we attempt to use high surface area electrodes to enhance the MS signal of CO2 to enable quantitative analysis of evolved CO2. To suppress the in-plane reaction distribution in the flow cell, we integrated an anion exchange membrane into the cell and arranged the counter electrode opposing the working electrode [3] (Fig. 1 (a)).CO-stripping voltammetry was performed to evaluate the CO2 detectability of the constructed DEMS system. The DEMS cell was composed of a commercial Pt/C electrode as the working electrode, a commercial Hg/HgO electrode as the reference electrode, a Pt mesh as the reference electrode, 1 mol dm–3 KOH aq as the electrolyte solution, and 1 mol dm–3 H2SO4 aq as the neutralizer. Figure 1 (b) shows the CO-stripping voltammogram and corresponding MS signal of CO2 (m/z = 44). MS signal of CO2 accompanied by the anodic CO oxidation current is clearly observed from 0.6 to 1.2 V vs. RHE. The calibration constant, which correlates the MS signal of CO2 to partial current for CO2 evolution reaction, is successfully obtained as 2.2 × 10–10, which shows that the DEMS system established in this study can quantitatively analyze CO2. Applications to the carbon corrosion reactions are also presented at the site.

(Invited)The Role of the Catalyst Microenvironment in the Electrochemical Reduction of Carbon Monoxide

Carbon monoxide is already an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petrochemical products. This can be performed under high temperature and pressure conditions in the Fischer-Tropsch process, but electrochemical methods also offer a possible way of forming different chemicals from carbon monoxide.Because of the low solubility of carbon monoxide in water, instead of the routinely used H-cells, its reduction must be performed in gas-fed electrolyzer cells, ensuring a short diffusion length for the reactant. However, even in such devices the surface of the catalyst (nano)particles is typically surrounded by a thin water shell under operating conditions, caused by various effects such as electrowetting, or wetting by the formed products. The practical insolubility of carbon monoxide (that is ca. 30 times lower compared to the solubility of CO2) makes it vital to ensure that the thickness of this hydration layer is minimized, hence the reactant can reach the catalysts' surface in gas phase, meanwhile just enough amount of a proton source – water – is in the immediate vicinity.The phase boundary between the catalyst particles, the liquid phase and the gas reactant can be engineered by using functional catalyst layer additives. Here we will demonstrate a commercial pore sealer for this purpose, ensuring the formation of C2+ products in CORR with high selectivity and rate.1 As no specific interaction between the polymer and the CO reactant was found, we assumed that the most important role of this polymer is to increase the hydrophobicity of the catalyst layer. To challenge this theory, various, systematically chosen polymeric materials were tested as catalyst binders to reveal any possible further contribution of certain motifs (e.g., functional groups, fluorinated backbone etc.), present in these polymers. The electrochemical results are contrasted with the detailed characterization of the structure, wetting and gas adsorption properties of the catalyst layer. Reference Kormányos, B. Endrődi, Z. Zhang, A. Samu, L. Mérai, G. F. Samu, L. Janovák, & C. Janáky (2023). EES Catalysis. https://doi.org/10.1039/D3EY00006K

(Invited) Selective and Efficient Electrochemical CO2 Reduction Reaction from Cu and Cu-M Binary Alloys

Electrochemical CO2 reduction reaction (CO2RR) has attracted a great deal of attention due to its potential to convert CO2 into valuable chemical fuels and feedstocks. The production of C2+ chemicals, such as ethylene and ethanol, from CO2RR is particularly important because of their large market demand. However, several challenges must be addressed before CO2RR can be commercially scaled up, including high overpotential, low selectivity, and poor CO2 solubility in aqueous solutions. In this presentation, I will discuss our recent efforts to overcome these challenges in CO2RR by using a gas diffusion electrode (GDE) to achieve a CO2RR current density of over 100 mA/cm2 in a flow reactor. First, I will highlight the crucial role of the local CO2RR environment in promoting C-C coupling on Cu surfaces, and I will present strategies for controlling this environment based on steady-state modeling and monodisperse Cu2O nanoparticles as a model catalyst system. Using this approach, we have been able to produce C2+ products, such as ethylene and ethanol, with a Faraday efficiency of over 70% at a current density of over 300 mA/cm2 in near-neutral electrolytes. Additionally, I will discuss the impact of alloying Cu with Ni and Zn on tailoring product selectivity. By introducing elements with different CO binding strengths, we can significantly alter the selectivity for hydrocarbons and alcohols. I will provide further details on these findings during the presentation.

Simultaneously promoting CO2 permeability and selectivity of polyethylene oxide membranes via introducing CO2-philic KAUST-7

To overcome the challenging trade-off between permeability and selectivity in polymer CO2 separation membranes, CO2-philic metal-organic framework (MOF) KAUST-7 was incorporated within polyethylene oxide (PEO)-type matrices to prepare mixed matrix membranes (MMMs). A cross-scale approach of quantum chemical calculations and molecular dynamics simulations was used to explore the behavior and mechanism of CO2 adsorption on KAUST-7. The strong affinity between KAUST-7 and CO2 enabled a dramatic increase in the CO2 solubility of MMMs. The 2 wt% KAUST-7 loaded MMM exhibited CO2 permeability and CO2/N2 selectivity of 608 Barrer and 75, respectively, representing 41.7% and 54% improvement compared to the neat membrane, exceeding the 2019 upper bound. Furthermore, long-term separation tests for 100 h demonstrated the stability of these membranes.

Enzymatic Carboxylation of Resorcinol in Aqueous Triethanolamine at Elevated CO2 Pressure.

The fixation of CO2 by enzymatic carboxylation for production of valuable carboxylic acids is one way to recycle carbon. Unfortunately, this type of reaction is limited by an unfavourable thermodynamic equilibrium. An excess of the C1 substrate is required to increase conversions. Solvents with a high CO2 solubility, such as amines, can provide the C1 substrate in excess. Here, we report on the effect of CO2 pressures up to 1100 kPa on the enzymatic carboxylation of resorcinol in aqueous triethanolamine. Equilibrium yields correlate to the bicarbonate concentration. However, inhibition is observed at elevated pressure, severely reducing the enzyme activity. The reaction yields were reduced at higher pressures, whereas at ambient pressure, higher yields were achieved. Overall, CO2 pressures above 100 kPa have been demonstrated to be counterproductive for improving the biotransformation, as productivity decreases rapidly for only a modest improvement in conversion. It is expected that CO2 carbamylation intensifies at elevated CO2 pressures, causing the inhibition of the enzyme. To further increase the reaction yield, the in situ product precipitation is tested by the addition of the quaternary ammonium salt tetrabutylammonium bromide.

Quantitative DEMS analysis of CO2 evolution reactions in alkaline electrolyte solutions

CO2 evolution is involved in various main and side reactions of electrochemical systems, such as carbon corrosion reactions and alcohol oxidation reactions. Differential electrochemical mass spectroscopy (DEMS) has been intensively applied to analyze the partial current of the CO2 evolution reaction in acidic and neutral electrolyte solutions. However, the quantitative analysis of the CO2 evolution reaction in alkaline electrolyte solutions has not been successful when catalyst-loaded carbon electrodes were applied, due to the high solubility of CO2 in the electrolyte. In this study, we develop a new DEMS system combining microreactor and ion exchange membrane to quantitatively analyze CO2 evolution reactions of catalyst-loaded carbon electrodes in alkaline electrolyte solutions. The calibration constant, which correlates the mass signal of m/z = 44 to the partial current of the CO2 evolution reaction, is successfully obtained from the Faradaic current and the mass signal of CO stripping voltammetry. We analyze carbon corrosion reactions of Pt and metal oxide-loaded carbon electrodes to demonstrate the effectiveness of the constructed system. The corrosion behavior of the Pt-loaded carbon is similar to that in the acidic electrolytes except for the onset potential of the carbon corrosion. La0.6Ca0.4CoO3 and Ca2FeCoO5 show electrochemical carbon corrosion activity, while La0.4Sr0.6MnO3 does not show distinct electrochemical carbon corrosion activity.

A facile synthesis of monolithic MOF single crystal for gas separation via a supersaturation strategy

Large-area metal–organic framework (MOF) single crystal membrane materials hold great appeal in gas separation field due to their outstanding separation selectivity and permeability. Nevertheless, it is currently difficult to prepare MOF single crystals large enough for gas separation tests owing to the limited manufacturing processes. In this work, we fabricate a self-supporting MOF single crystal (Co-btec SC) membrane with 0.3 × 0.1 cm2 dimension via a facile supersaturation synthesis strategy. Benefiting from the one-dimensional (1D) transmission pathway and three-dimensional (3D) connection network, the obtained Co-btec SC has ultra-high permeability of 47,647 Barrer. Besides, the H2O molecules firmly filled in the pore channels greatly improve the affinity and solubility for CO2, and thus Co-btec SC yields CO2 preferential permeation in CO2/H2 mixture with superior CO2/H2 selectivity of 18.79. In addition, the Co-btec SC shows dramatic high-temperature and high-humidity separation stabilities. To demonstrate the versatility of this strategy, we also successfully fabricated hydrogen-bonded organic framework single crystals (HOF SCs) with the size of about 0.4 cm. This supersaturation strategy opens a new way to fabricate the large-area MOF single crystal membranes.

Polymer Modification Strategy to Modulate Reaction Microenvironment for Enhanced CO2 Electroreduction to Ethylene

AbstractModulation of the microenvironment on the electrode surface is one of the effective means to improve the efficiency of electrocatalytic carbon dioxide reduction (eCO2RR). To achieve high conversion rates, the phase boundary at the electrode surface should be finely controlled to overcome the limitation of CO2 solubility in the aqueous electrolyte. Herein, we developed a simple and efficient method to structure electrocatalyst with a superhydrophobic surface microenvironment by one‐step co‐electrodeposition of Cu and polytetrafluoroethylene (PTFE) on carbon paper. The super‐hydrophobic Cu‐based electrode displayed a high ethylene (C2H4) selectivity with a Faraday efficiency (FE) of 67.3 % at −1.25 V vs. reversible hydrogen electrode (RHE) in an H‐type cell, which is 2.5 times higher than a regular Cu electrode without PTFE. By using PTFE as a surface modifier, the activity of eCO2RR is enhanced and water (proton) adsorption is inhibited. This strategy has the potential to be applied to other gas‐conversion electrocatalysts.

Mixed matrix membranes based on NbOF52− anion-pillared porous MOFs for efficient CO2 separation

CO2 capture and storage technologies are crucial for environmental conservation and sustainable progress. To overcome the challenging trade-off between permeability and selectivity in polymeric CO2 separation membranes, we innovatively fabricated mixed matrix membranes (MMMs) by introducing three different NbOF52− anion-pillared porous metal–organic frameworks (MOFs), namely NbOFFIVE-2-Cu-i, NbOFFIVE-2-Ni-i, and NbOFFIVE-bpy-Ni. The CO2 capture performance of the three MOFs was investigated for the first time, and the ideal adsorption solution theory (IAST) method was used to predict the CO2 separation selectivity. Density functional theory (DFT) calculations confirmed that the interaction energy between NbOFFIVE-2-Cu-i and CO2 is the highest among the three MOFs. This is due to the optimal pore dimensions and strong Cδ+ … Fδ− electrostatic interaction between the C atoms in CO2 molecules and the F atoms in NOFFIVE-2-Cu-i. The introduction of the three MOFs into the MMMs led to an increase in CO2 solubility, resulting in enhanced CO2 permeability and selectivity. The MMM loaded with 2 wt% of NbOFFIVE-2-Cu-i exhibited exceptional CO2 permeability and CO2/N2 ideal selectivity values of 578 Barrer and 70, respectively, representing enhancements of 39 % and 29 % compared to neat membrane, and exceeding the upper bound established in 2019.

Predicting the solubility of gases in imidazolium-based ionic liquids with SAFT-VR Mie EoS by a novel approach based on COSMO

This theoretical study presents a novel approach to predict the solubility of CO2 and CH4 in Ionic Liquids (ILs) under various pressures and temperatures using the predictive SAFT-VR Mie equation of state combined with the COSMO calculations. This approach involves estimating the segment number, diameter, and segment energy of the ionic liquid using the molecular volume from the COSMO model. The 2B and 4C association schemes were examined for ILs. The predicting results obtained through this innovative strategy demonstrate excellent accuracy in predicting gas solubility. The average absolute relative deviation of the most optimal association scheme scenario ranges from 4.8 to 14.2% for CO2 and 5.7 to 6.4% for CH4, respectively, without the need for binary interaction parameters.

Preparation of ionic liquids amine hybrid solvents, characterization for CO2 absorption, and kinetic performance

The thermo-physical characteristics of an ionic liquid-amine hybrid solvent were studied in this work as a result of its potential use in the CO2 absorption process. The hybrid solvents were developed by mixing 30 wt% MDEA with ionic liquid at different concentrations of 5 wt%, 10 wt%, 15 wt% and 20 wt%. Three imidazolium-based ILs were investigated: 1-butyl-3-methylimidazolium dicyanamide [bmim][DCA], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate [bmim][TfO. Aqueous ionic liquid-amine hybrid solvent's density, surface tension, refractive index, viscosity and were studied between 25 °C and 70 °C with a regular interval of 5 °C. Whereas the influence of temperature on viscosity is negligible beyond 65 °C and the influence of temperature changed certain physicochemical properties. Furthermore, high-pressure solubility tests were conducted at a fixed temperature of 30 °C to determine the solubility of CO2 in hybrid media at pressures ranging from 2 bar to 50 bar. The results showed that the CO2 solubility of the different ionic liquid-amine hybrid systems decreases in the following sequence: [bmim][TfO] + MDEA > [bmim][DCA] + MDEA > [bmim][Ac] + MDEA. It was also found out that the optimum concentration of ionic liquids in the solution is 10 wt%. The kinetics study of the hybrid solvents was studied as a function of concentration, and experimentally determined that 10 wt% [bmim][TfO] exhibited the fast CO2 absorption kinetics. The kinetics performance study was further conducted as a function of pressure, and the highest absorption rate was recorded at 50 bar as expected. Overall, the addition of ionic liquids was verified to improve the CO2 absorption and thus it was reported that ionic liquid-amine hybrid solvent is an auspicious solvent for CO2 removal in the future.