Interfacial Activity Research Articles

MoB2 modified g-C3N4: A Schottky junction with enhanced interfacial redox activity and charge separation for efficient photocatalytic H2 evolution

The g-C3N4 material, which exhibits a sensitivity to visible light and has a band position that is appropriate for the photoreduction of H2, has garnered significant interest. However, the ability of g-C3N4 to use light for photocatalysis is restricted due to its insufficient capacity to absorb light and its poor reaction kinetics on the surface. The researchers opted for the metallic MoB2 to create a Schottky junction coupled with g-C3N4. The incorporation of MoB2 nanoparticles onto g-C3N4 enhances its light absorption capacity and promotes the efficient separation and transfer of photogenerated charge. In addition, MoB2 nanoparticles served as active sites to accelerate H2 evolution. Compared to g-C3N4, the MoB2@g-C3N4 composite exhibited a nearly 51-fold increase in H2 production rate, indicating a significant improvement in photocatalytic activity. The present investigation demonstrated the potential of metallic MoB2 as a modified material during a photocatalytic H2 evolution reaction.

Synthesis and emulsion stability of salt resistant viscosity reducer for heavy oil reservoirs with varying salinities

To address the inadequate salt resistance of viscosity reducers and their limited applicability to reservoirs with single salinity, we synthesized salt-resistant viscosity reducers PANxAn in this study. These compounds were derived from fatty alcohol polyoxyethylene ether acrylate, N-alkyl acrylamide, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. The structures were identified using nuclear magnetic hydrogen spectroscopy. We investigated the effects of the hydrophilic group ethoxy-chain length (n = 14, 16, 18, 20 and 22) and hydrophobic group alkyl-chain length (x = 12, 14, 16, and 18) on the salt resistance, interfacial activity, wettability, interfacial viscoelasticity and emulsification viscosity reduction performance of the viscosity reducers. Futher, the structures of the viscosity reducers which can adapt to different salinities were determined. Based on the emulsification viscosity reduction effect, PAN14A16, PAN12A16, PAN12A18, PAN12A20/PAN16A16 and PAN12A22/PAN18A16 adapted to salinities range of 2 × 104-6 × 104, 4 × 104-8 × 104, 6 × 104-10 × 104, 8 × 104-12 × 104 and 10 × 104-14 × 104 mg/L, respectively. At the optimal salinity, PANxAn reduced the oil–water interfacial tension from 28.3 to 5.0 mN/m, dynamic contact angle from 130.0° to 61.0°, and heavy oil viscosity from 454.6 to 60.0 mPa·s with a viscosity reduction rate of 86.80 %. The synthesis of salt-resistant PANxAn provides theoretical guidance and application value for enhancing the recovery efficiency of viscosity-reducer flooding in high-salinity heavy oil reservoirs.

One-Pot Synthesis of Amphipathic Esters for Demulsification of Water-in-Crude Oil Emulsions.

The current work aims to synthesize new amphipathic compounds, TGHA and PGHA, and investigate their demulsification performance (DP) in water-in-crude oil emulsions. Their chemical structures, thermal stability, interfacial activity, and micelle formation were investigated by different techniques. The bottle test method was used to investigate the effect of demulsifier concentration, water content, temperature, and demulsification time (DT) on the DP of TGHA and PGHA compared to a commercial demulsifier (CD). The results indicated that these parameters have a noticeable impact on the DP of TGHA and PGHA. The results also showed that TGHA exhibited higher DP than PGHA at all investigated parameters, which could be explained by increasing its hydrophobicity due to lower oxyethylene units in its structure than PGHA. An increase in these units means increased hydrophilicity, which led to obstruction of PGHA molecule diffusion in crude oil as a continuous phase. Moreover, TGHA gave a comparable DP with CD, as it gave a higher DP and shorter DT than CD at a higher water content (50%), while the latter achieved the highest DP and the shortest DT at a low water content (10%).

Study on the Alkali-Free Three-Component Flooding System in the Daqing Oilfield.

ASP flooding is an important method to further improve oil recovery by a large margin. At present, it has entered the stage of industrial application, but there are still problems of scaling in the injection production system and high production maintenance costs. Based on the industrialized mature technology of weak alkali ASP flooding, sodium chloride is used to replace sodium carbonate, and the alkali-free three-component flooding (TC) system in the Daqing Oilfield is developed by mixing with petroleum sulfonate and partially hydrolyzed polyacrylamide. Based on the experiments of viscosity increasing, interface performance, stability, adsorption, and oil displacement effect, the differences between the alkali-free TC system and the weak alkali ASP system are compared and analyzed. The laboratory research results show that both systems are basically the same in terms of viscosity, viscoelasticity, shear resistance, interfacial activity, stability, and flowability. Due to the lack of alkaline water, the adsorption, emulsification, and oil displacement performance of the alkali-free TC system is slightly lower than that of the weak alkali ASP system. The recovery factor of core flooding can be increased by 27.31% over water flooding, which is 2.56 percentage points lower than that of the weak alkali ASP system. On the premise of the same 1% EOR effect, the agent cost of the alkali-free system is 17.02% lower than that of the alkali ASP system. This article innovatively verifies the feasibility of using NaCl instead of Na2CO3 and explains the mechanism of significantly improving oil recovery in composite systems under alkali-free conditions from the ion level. However, the emulsification effect of the alkali-free TC system is relatively weak. The next step of research would be to consider adding an E-surfactant to enhance the emulsification performance of the composite system. By improving the system composition, technical references are provided for the efficient development of other terrestrial sandstone oilfields.

One-Pot synthesis and interfacial activity of imidazolium ionic liquid surfactants with double-chain hydrophobic

Three double-chain imidazolium ionic liquid surfactants (ILS) with varying alkyl lengths, namely [C10mimC10][OAc], [C12mimC12][OAc], and [C14mimC14][OAc], were synthesized via the one-step Debus-Radziszewskireaction. The chemical structures of these three ILS were confirmed through FT-IR, 1H NMR and ESI-MS analyses. Their surface/interface activity, wetting ability, thermal stability, and aggregation properties were investigated. The results indicated that the presence of double-chain hydrophobic groups in ILS exerted a significant influence on their surface/interface activity. Surface activity and micellization properties were assessed using surface tension measurements, revealing that the micellization process of double-chain ILS was more favorable compared to single-chain ILS. Among the three ILS examined, [C14mimC14][OAc] exhibited the lowest surface tension and critical micelle concentration (CMC) values, measuring 29.07 mN/m and 1.64 × 10-2 mmol/L, respectively. Solutions containing approximately 50 ppm of these ILS could reduce interfacial tension to below 1 mN/m. Additionally, the contact angle decreased to less than 90° within 90 s. The formation of aggregates in aqueous solutions was found to be influenced by the number of CH2 units present in the different ILS molecules.

Built-in Electric Field Promotes Interfacial Adsorption and Activation of CO2 for C1 Products over a Wide Potential Window.

The unsatisfactory adsorption and activation of CO2 suppress electrochemical reduction over a wide potential window. Herein, the built-in electric field (BIEF) at the CeO2/In2O3 n-n heterostructure realizes the C1 (CO and HCOO-) selectivity over 90.0% in a broad range of potentials from -0.7 to -1.1 V with a maximum value of 98.7 ± 0.3% at -0.8 V. In addition, the C1 current density (-1.1 V) of the CeO2/In2O3 heterostructure with a BIEF is about 2.0- and 3.2-fold that of In2O3 and a physically mixed sample, respectively. The experimental and theoretical calculation results indicate that the introduction of CeO2 triggered the charge redistribution and formed the BIEF at the interfaces, which enhanced the interfacial adsorption and activation of CO2 at low overpotentials. Furthermore, the promoting effect was also extended to CeO2/In2S3. This work gives a deep understanding of BIEF engineering for highly efficient CO2 electroreduction over a wide potential window.

An underwater vest containing an antioxidant MXene hydrogel for sensitive recognition of fish locomotion

The perception of fish locomotion is important for understanding their adaptive behaviors and ethological characteristics. However, the main strategy used for extracting fish attitudes involves the use of a vision-based monitoring system, which is limited in its range of observation and cannot perform tracking for long times. Here, we report the use of a wearable tagging electronic device, referred to as an underwater vest, to capture the surrounding flow field disturbances triggered by swimming or momentary postural changes. All of these goals were achieved by integrating a pair of pseudocapacitive pressure-sensing units and a flexible circuit board. Notably, additional conditions, such as variable hydraulic pressures and minimal changes in fish posture, require high stability and sensitivity of the sensing units. Thus, hybrid hydrogel electrodes were developed through cross-linking MXene with holey-reduced graphene oxide nanosheets and further modification with 1-ethyl-3-methylimidazolium dicyanamide ionic liquids, which increased the interfacial capacitance and long-term interfacial activity of the MXene. Consequently, the sensing unit exhibited ultrahigh sensitivity (Smax~136,207 kPa−1) in an aquatic environment for 60 days and superior high-pressure resolution (10 Pa) within a wide working range of 1 MPa. Ultimately, an underwater vest integrated with such sensing units clearly distinguished and recorded fish locomotion. We believe that the designed device may open avenues in flow field monitoring and ocean current detection and provide new insights into the development of sensitive underwater tagging.

Greatly improved energy storage density of SrO2–BaO2–Nb2O5–SiO2–Al2O3–B2O3 glass ceramics by various amount CeO2 doping

Glass ceramic dielectric materials with high power density and high energy density have important application value in the miniaturization and integration of lightweight pulse power devices. In this work, SrO2–BaO2–Nb2O5–SiO2–Al2O3–B2O3 glass ceramics doped with various contents of CeO2 were prepared via high-temperature melting combined with temperature-controlled crystallization process. Results showed that CeO2 doping increased the content of Ba0.27Sr0.75Nb2O5.78 tungsten bronze phase precipitate from the glass matrix in glass ceramics (from 55.7% to 82.2%), thereby increasing dielectric constant of SrO2–BaO2–Nb2O5–SiO2–Al2O3–B2O3 glass ceramics (from 66.5 to 101.9). Besides that, CeO2-doped ceramics exhibited excellent temperature stability and low loss (below 0.015). The highest breakdown strength (1590 kV/cm) and energy density (12.88 J/cm3) were achieved in the ceramic with a CeO2 doping concentration of 3.0 mol.%, being 3.03 times higher than those in undoped glass ceramic. The increase in energy density of the ceramics was attributed to moderate CeO2 doping concentration that improved the crystallinity (from 83.8% to 89.8%) and reduced the interfacial activation energy of the glass ceramics.

Ultralow interfacial tension achieved by extended anionic surfactants with a short hydrophobic chain

Extended surfactant is a new type of oil displacement agent with excellent performance in enhanced oil recovery (EOR). In this paper, the novel extended surfactants with short hydrophobe (ethylhexyl) have been studied. The dynamic interfacial tensions (IFTs) between extended surfactant (C8PxEyC) solutions and n-alkanes were measured by the spinning drop method. The effect of surfactant concentration, polyoxypropylene (PO) numbers, polyoxyethylene (EO) numbers and electrolyte on the IFTs were investigated. The experimental results show that the interfacial activity of the extended surfactants mainly depends on the PO groups, and the short hydrophobe extended anionic surfactant shows the similar behavior of reducing IFT to that of long alkyl chain one. The IFTs decrease with an increase of the PO numbers against n-alkanes, and an increase of the EO numbers leads to the destruction of the tight arrangement of the adsorption film because the size of EO group is smaller than that of PO group, which results in an increase of IFT. The addition of electrolyte can reduce the IFTs by weakening the electrostatic repulsion between surfactant molecules at the interface, but it has little effect on its HLB. The long EO chain of extended surfactant prevents divalent cation from binding two surfactant counterions, which results in the little effect on reducing IFT. This study is of great significance for the insight of extended surfactants and their application in high-salt reservoirs.

Dumbbell-shaped polymeric nanoparticles with one-side anchored Pd-clusters for efficient catalytic hydrogenation at biphasic interfaces

Pickering interfacial catalysts incorporated with amphiphilic architecture significantly expand the sustainability of green catalysis systems. In this work, we present precise and well-designed dumbbell-shaped Janus-structured polymeric nanoparticles with one-side anchored palladium clusters (DB-JPP-Pd) as Pickering interfacial catalyst for static hydrogenations. The large wettability difference of each lobe renders the prominent amphiphilicity of the dumbbell-shaped DB-JPP-Pd. The amphiphilic Janus catalyst displays excellent interfacial activity and extensively reduces the interfacial tension from 34.06 ± 0.13 to 20.54 ± 0.31 mN/m, promoting the formation of a more stable Pickering emulsion than that of the bulk PS-Pd catalyst, which can continuously provide a large interfacial area and shorten the molecular mass transfer distance during the reaction process. As a result, the DB-JPP-Pd catalyzed nitroarene reduction reaction exhibits a normalized reaction rate constant (knor) of 3.39 min−1⋅g−1⋅L under static conditions, which is 56.5 times higher than that of bulk PS-Pd. The constructed Pickering interfacial catalysis (PIC) system converts all the nitrobenzene into aniline within three minutes and possesses excellent selectivity in hydrogenations of different nitro aromatics. In addition, the emulsion catalytic system was conveniently recycled for ten consecutive runs. Hence, this unique amphiphilic dumbbell-shaped catalyst effectively develops an efficient static biphasic catalysis system.

In Situ Growth of Interfacially Nanoengineered 2D-2D WS2/Ti3C2Tx MXene for the Enhanced Performance of Hydrogen Evolution Reactions.

In line with current research goals involving water splitting for hydrogen production, this work aims to develop a noble-metal-free electrocatalyst for a superior hydrogen evolution reaction (HER). A single-step interfacial activation of Ti3C2Tx MXene layers was employed by uniformly growing embedded WS2 two-dimensional (2D) nanopetal-like sheets through a facile solvothermal method. We exploited the interactions between WS2 nanopetals and Ti3C2Tx nanolayers to enhance HER performance. A much safer method was adopted to synthesize the base material, Ti3C2Tx MXene, by etching its MAX phase through mild in situ HF formation. Consequently, WS2 nanopetals were grown between the MXene layers and on edges in a one-step solvothermal method, resulting in a 2D-2D nanocomposite with enhanced interactions between WS2 and Ti3C2Tx MXene. The resulting 2D-2D nanocomposite was thoroughly characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses before being utilized as working electrodes for HER application. Among various loadings of WS2 into MXene, the 5% WS2-Ti3C2Tx MXene sample exhibited the best activity toward HER, with a low overpotential value of 66.0 mV at a current density of -10 mA cm-2 in a 1 M KOH electrolyte and a remarkable Tafel slope of 46.7 mV·dec-1. The intercalation of 2D WS2 nanopetals enhances active sites for hydrogen adsorption, promotes charge transfer, and helps attain an electrochemical stability of 50 h, boosting HER reduction potential. Furthermore, theoretical calculations confirmed that 2D-2D interactions between 1T/2H-WS2 and Ti3C2Tx MXene realign the active centers for HER, thereby reducing the overpotential barrier.

Effects of different oil fractions and tannic acid concentrations on konjac glucomannan-stabilized emulsions

Polysaccharide-stabilized emulsions have received extensive attention, but emulsifying activity of polysaccharides is poor. In this study, konjac glucomannan (KGM) and tannic acid (TA) complex (KGM-TA) was prepared via non-covalent binding to increase the polysaccharide interfacial stability. The emulsifying stabilities of KGM-TA complex-stabilized emulsions were analyzed under different TA concentrations and oil fractions. The results indicated that hydrogen bonds and hydrophobic bonds were the main binding forces for KGM-TA complex, which were closely related to TA concentrations. The interfacial tension of KGM-TA complex decreased from 20.0 mN/m to 13.4 mN/m with TA concentration increasing from 0 % to 0.3 %, indicating that TA improved the interfacial activity of KGM. Meanwhile, the contact angle of KGM-TA complex was closer to 90° with the increasing TA concentrations. The emulsifying stability of KGM-TA complex-stabilized emulsions increased in an oil mass fraction-dependent manner, reaching the maximum at 75 % oil mass fraction. Moreover, the droplet sizes of KGM-TA complex-stabilized high-internal-phase emulsions (HIPEs) decreased from 82.7 μm to 44.7 μm with TA concentration increasing from 0 to 0.3 %. Therefore, high TA concentrations were conducive to the improvement of the emulsifying stability of KGM-TA complex-stabilized HIPEs. High oil mass fraction promoted the interfacial contact of adjacent droplets, thus enhancing the non-covalent binding of KGM molecules at the interfaces with TA as bridges. Additionally, the high TA concentrations increased the gel network density in the aqueous phase, thus enhancing the emulsifying stability of emulsions. Our findings reveal the mechanisms by which polysaccharide-polyphenol complex stabilized HIPEs. Therefore, this study provides theoretical basis and references for the developments of polysaccharide emulsifier with high emulsifying capability and high-stability emulsions.

Synergy evaluation of flavonoid glycosides from Camellia oleifera cake and ionic surfactants on the stability of oil-in-water emulsions

Compared with synthetic surfactants, amino acid surfactants (sodium N-lauroylsarcosinate, SLS) and natural products (flavonoid glycosides from Camellia oleifera cake, FG) have renewability, lower toxicity, and biodegradability, which can reduce energy consumption and environmental pollution during emulsion preparation. Storage time and lipid oxidation are important indicators for evaluating the environmental adaptability of emulsions. However, the effect of complex systems (surfactants and flavonoids) on emulsion performance and its related mechanisms have not yet been thoroughly studied. The oxidative stability, physical stability, and interaction mode of FG-ionic surfactants (SLS/CTAB)-stabilized oil-in-water (O/W) emulsions were explored. The results indicated that FG displayed excellent antioxidant and emulsifying capacity without negative hemolysis. Moreover, FG contributed to the interfacial activity of ionic surfactants. The optimum synergistic ratio of SLS/CTAB-FG was 0.167/0.091. The presence of FG alleviated the stratification of cream volume and retarded Ostwald ripening and droplet coalescence. After storage, the FG-SLS-stabilized emulsions showed the smallest droplet size and the largest emulsion volume. Moreover, the addition of FG effectively reduced the production of harmful substances such as 2-thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides. A meaningful discovery was that oxidative stability depended strongly on the interaction mechanism between FG and surfactants. FG was more useful for improving the oxidative stability of anionic surfactant-stabilized emulsions. Overall, this study demonstrates that Camellia oleifera cake can serve as an inexpensive and eco-friendly renewable resource for natural emulsifiers and antioxidants, and provides theoretical guidance for its more effective utilization.

Liquid Marbles and Drops on Superhydrophobic Surfaces: Interfacial Aspects and Dynamics of Formation: A Review.

Liquid marbles (LMs) are droplets encapsulated with powders presenting varied roughness and wettability. These LMs have garnered a lot of attention due to their dual properties of leakage-free and quick transport on both solid and liquid surfaces. These droplets are in a Cassie-Baxter wetting state sitting on both roughness and air pockets existing between particles. They are also reminiscent of the state of a drop on a superhydrophobic (SH) surface. In this review, LMs and bare droplets on SH surfaces are comparatively investigated in terms of two aspects: interfacial and dynamical. LMs present a fascinating class of soft matter due to their superior interfacial activity and their remarkable stability. Inherently hydrophobic powders form stable LMs by simple rolling; however, particles with defined morphologies and chemistries contribute to the varied stability of LMs. The factors contributing to this interesting robustness with respect to bare droplets are then identified by tests of stability such as evaporation and compression. Next, the dynamics of the impact of a drop on a hydrophobic powder bed to form LMs is studied vis-à̀-vis that of drop impact on flat surfaces. The knowledge from drop impact phenomena on flat surfaces is used to build and complement insights to that of drop impact on powder surfaces. The maximum spread of the drop is empirically understood in terms of dimensionless numbers, and their drawbacks are highlighted. Various stages of drop impact-spreading, retraction and rebound, splashing, and final outcome-are systematically explored on both solid and hard surfaces. The implications of crater formation and energy dissipations are discussed in the case of granular beds. While the drop impact on solid surfaces is extensively reviewed, deep interpretation of the drop impact on granular surfaces needs to be improved. Additionally, the applications of each step in the sequence of drop impact phenomena on both substrates are also identified. Next, the criterion for the formation of peculiar jammed LMs was examined. Finally, the challenges and possible future perspectives are envisaged.

Structure-induced interfacial activation convoying the CO-relayed conversion of CO2 to dimethyl carbonate

The recognition of structure-induced interfacial activation in heterogenized molecule catalysts is essential to steer CO2 value-added electroconversion but remains inadequate. Herein, through designing three congeneric Co-N4 model molecules (Co-CPY, Co-TAA and Co-PHE) with recognizable steric configurations, we systematically investigated the impact of structure-induced interfacial activation on promoting CO2 electroconversion. Concretely, the Co-CPY/CNTs, featuring highly planar and conjugated molecules immobilized onto CNTs, delivers an ultra-high current density and enables near-unity Faradaic efficiency for CO2 electroconversion, exceeding the counterparts. The theoretical and spectrographic findings demonstrate that the Co-CPY/CNTs not only creates the adaptive interfaces with strong communication to greatly expedite electron transfer but also reconstructs the electronic structures of active Co-N4 units to effectively promote the formation of intermediates. Furthermore, the electroconversion of CO2 to dimethyl carbonate was reliably performed with a high yield of 96 μmol cm–2 h−1 through paired tandem electrosynthesis, highlighting the superior expansibility of Co-CPY/CNTs.

Tailoring Nanostructured Cellulose for Efficient Pickering Emulsions Stabilization

AbstractNanostructured celluloses, nanofibrils (CNFs) and nanocrystals (CNCs), are prepared through TEMPO‐mediated oxidation by controlling the intensity of the process modulated by catalyst concentration and processing time. These nanomaterials are evaluated as stabilizers for Pickering emulsions, fabricated using high‐pressure homogenization (HPH). Both CNFs and CNCs exhibit efficient steric and electrostatic stabilization of oil‐in‐water (O/W) emulsions. CNFs display strong inter‐droplet interactions, leading to the formation of a 3D fibrous network emulsion with higher viscosity compared to CNCs‐stabilized emulsions. However, CNFs also show a higher tendency toward flocculation, due to fibrils’ entanglement in the continuous phase. Interestingly, the HPH treatment has a notable impact on the CNFs’ interfacial layer, enhancing the emulsifying ability of CNFs and improving stability against coalescence. Conversely, CNCs‐stabilized emulsions exhibit lower viscosity but demonstrate higher interfacial activity and stabilization capability. Remarkably, no phase separation during 10 months of refrigerated storage, indicating excellent long‐term stability. Importantly, the HPH treatment does not significantly change the emulsifying ability of CNCs. In conclusion, this study highlights the possibility of obtaining nanocelluloses (NCs) with tailored emulsifying properties by regulating the intensity of TEMPO‐mediated oxidation applied to pulp cellulose. These findings open up new opportunities for the development of innovative ingredients for the food and cosmetic industries.

Pickering stabilization of water-in-crude oil emulsions by paraffin wax crystals: Insights from X-ray scattering

Previous studies suggest asphaltenes are active materials at the oil-water interface, affecting the formation and stability of crude oil emulsions. However, even oils of low asphaltene content generate stable emulsions, indicating the involvement of other oil fractions. Due to the role of paraffin waxes as Pickering stabilizers or gel network formers in emulsions from other applications, this study explores their stabilization capacity in water-in-oil (W/O) emulsions and their interaction with other fractions with interfacial activity. The extraction and physicochemical characterization of paraffin waxes from two Brazilian crude oils allowed us to correlate their properties with the emulsification of both crude and model oils. Removal of asphaltenes enhances emulsion stability. Emulsion preparation with crude oils without waxes and asphaltenes demonstrates the participation of other amphiphilic components in emulsion formation, whereas waxes are necessary for their stabilization. Experiments with emulsions formed by a model oil confirmed the combined action of waxes and an amphiphilic material in the formation and stabilization of the interfacial film. However, the combination of waxes and asphaltenes are ineffective. Small-angle X-ray scattering (SAXS) analysis revealed that waxes only form a lamellar structure when highly purified, suggesting Pickering stabilization rather than the formation of a gel network. In conclusion, polar oil fractions other than asphaltene play a crucial role in emulsion formation, whereas paraffin wax provides Pickering stabilization, even beyond the wax appearance temperature (WAT). This study enhances our understanding of the mechanisms governing waxy Brazilian crude oil emulsions.

Biphasic interfacial functioning improvement using naturally derived Hop and Dill surfactants in carbonate reservoirs

This study mainly focuses on the application of environmentally friendly surfactants in enhanced oil recovery (EOR). Two natural and environmentally friendly surfactants of Hop and Dill were introduced to observe their visions of fluid/fluid/rock interfacial activity of surfactant solutions as ion tuned EOR method. Investigations of interfacial tension (IFT) reduction and wettability alteration toward a water-wetting tendency were conducted to evaluate the improvement of oil recovery factor. Dynamic displacement tests of carbonate porous medium flooding including both secondary and tertiary flooding were conducted to observe the validity of IFT reduction and wettability alteration (contact angle decrease, CA) effects. IFT measurements showed that Dill and Hop surfactants can reduce the initial IFT of 28 mN/m to 2.443 and 5.614 mN/m, respectively. Ion concentration tuning showed that 10,000 ppm of NaCl is the optimum concentration that could enhance the optimization value of Dill surfactant from 91.27% to 92.8% (with 17.46% improvement compared with CMC of Dill). In addition, NaCl salt at the same concentration improved the effectiveness of Hop surfactant by 6.1%. Meanwhile, the used surfactants reduced the contact angle from 151° to 75° and 65° for Dill and HOP, respectively. Ion tuning showed that 10,000 ppm of salinity effect could enhance the optimization by Dill and Hop to 70.86 and 71.54%, respectively. Zeta potential measurements proved that the contact angle results in a complementary manner. Core flood tests validated previous results through the improvements in the recovery of oil by 8.56 and 10.11% original oil in place (OOIP) for HOP and Dill natural surfactants, respectively.

Interfacial chemical mechanisms of brine salinity affecting the CO2 foam stability and its effect on the sequestration capacity of CO2 in deep saline aquifer

CO2 foam flooding is an important method to expand the sweep scope of CO2 and significantly improve the ability of sequestrate CO2 in saline aquifer. Salinity is an important factor affecting the CO2 foam stability. In this study, it was found that the stability of CO2 foam prepared by alkyl polyglycoside APG-0810 was effectively improved by increasing the salinity. Molecular dynamics studies showed that increasing salinity promoted the adsorption of APG-0810 molecules at the CO2-water interface and enhanced the degree of inter-entanglement between alkyl chain segments, which dramatically increasing the CO2-water interfacial activity and liquid film strength. The enrichment degree of metal ions around the APG-0810 hydrophilic group also enhanced with the increase of salinity, which improves the disjoining pressure of the bubble liquid film. The binding ability of the hydrophobic groups of APG-0810 on CO2 molecules was enhanced, which inhibited the diffusion process of CO2 molecules inside the bubble. Subsequently, the influence rules of salinity on the CO2 foam rheology in the core were studied, and finds that increasing salinity increase the transition foam quality and the corresponding maximum viscosity. The improvement of liquid film strength reduces the probability of bubble aggregation inside the core, allowing a sufficient number of small-sized bubbles to be trapped by the pores, strengthening the superposition of Jamin effect and expanding the CO2 sweep scope in saline aquifer. In addition, we found that the zero-shear viscosity and yield stress of CO2 foam are positively correlated with salinity, which means that CO2 foam has a higher blocking ability for preferential channel for high-salinity saline aquifer, and the bubble cluster trapped by the capillary force will have a higher starting-pressure, improving the safety of CO2 sequestration in saline aquifer.

Regeneration of Fe-Co gel-ball: Designing uniform heterojunction with double N-doped carbon towards high-rate energy-storage abilities

Captured by high theoretical capacity and energy density, metal-sulfides have been regarded as strong candidates, but they still suffer from by polysulfides shuttling, volume swelling and slow kinetics. Herein, through the utilization of sol-gel precursors, the interesting heterostructure materials could be successfully prepared with multi-carbon layers, displaying uniform particle size and improved conductivities. Benefitting from the limitation and adsorption of carbon, the moving behaviors of polysulfides are effectively inhibited, accompanying with the alleviating volume expansion. More interestingly, the enhanced degree of interfacial redox reactions and electrochemical kinetics were noted, mainly resulted from the improved interfacial activities. As expected, used as Na-storage abilities, the capacity of optimized samples could reach up to 949.1 mAh g−1 at 0.2 A g−1, with remarkable coulombic efficiency 91.1 %. Moreover, the excellent capacity retention could be remained about 90.6 % even after 100 loops. Supported by DFT calculations, the adsorption energy of Na-atoms behaviors could be noted for heterostructure. Assisted by detailed kinetic analysis, their great charging capacity mainly originate from quickened interfacial ions/e− transfer rates and accelerated conversion-reaction kinetics. Given this, this work is expected to reveal the in-depth insight of energy-storage behaviors of hetero-structure, and offer effective designing strategies of sodium-ion storage systems.