Free Energy Of Adsorption Research Articles

Partially Interstitial Silicon‐Implanted Ruthenium as an Efficient Electrocatalyst for Alkaline Hydrogen Evolution

To enhance the alkaline hydrogen evolution reaction (HER), it is crucial, yet challenging, to fundamentally understand and rationally modulate potential catalytic sites. In this study, we confirm that despite calculating a low water dissociation energy barrier and an appropriate H adsorption free energy (ΔG*H) at Ru‐top sites, metallic Ru exhibits a relatively inferior activity for the alkaline HER. This is primarily because the Ru‐top sites, which are potential H adsorption sites, are recessive catalytic sites, compared with the adjacent Ru‐hollow sites that have a strong ΔG*H. To promote the transformation of Ru‐top sites from recessive to dominant catalytic sites, interstitial Si atoms are implanted into the hollow sites. However, complete interstitial implantation leads to a high water dissociation energy barrier at the RuSi intermetallic surface. Thus, we present a partial interstitial incorporation strategy to form a Ru–RuSi heterostructure that not only converts the Ru‐top sites from recessive to dominant catalytic sites but also preserves the low water dissociation energy barrier at the Ru surface. Moreover, the spontaneously formed built‐in electric fields bidirectionally optimize the adsorption ability of the Ru sites, thereby greatly reducing the thermodynamic energy barrier and enhancing the alkaline HER.

N-Doped Carbon-Incorporated Cobalt-Iron Mixed-Metal Phosphide Nanoboxes as Efficient Bifunctional Catalysts for Overall Water Splitting.

Optimizing the composition and structure of nanocatalysts is an efficient approach to achieving the top electrocatalytic performance. However, the construction of hollow nanocomposites composed of metal phosphides and highly conductive carbon to promote the electrocatalytic performance of metal phosphide-based catalysts is rarely reported. Herein, a CoFeP/C nanobox nanocomposite consisting of Co-Fe mixed-metal phosphides and N-doped carbon was successfully fabricated through an ion-exchange phosphidation strategy derived from ZIF-67 nanocubes. Benefiting from the synergistic effects between multiple components and the unique hollow structure, CoFeP/C nanoboxes can catalyze the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with high activity and stability. Furthermore, in the construction of an alkaline water electrolyzer using CoFeP/C nanoboxes as both OER and HER catalysts, they were capable of efficiently splitting water with a current density of 10 mA cm-2 achieved by applying only 1.62 V of cell voltage and exhibited outstanding durability. Density functional theory calculations demonstrate that synergistic effects among multiple components in CoFeP/C nanoboxes can lower the hydrogen adsorption free energy of the HER and OER energy barrier of the rate-determining step, thus promoting the catalytic reactions. The design and synthesis of CoFeP/C nanoboxes highlight the importance of the composition and structural characteristics in achieving high-performance water electrolysis.

Synthesis, characterization, biodegradation, and evaluation of the surface‐active properties of non‐ionic gemini surfactants derived from lauryl diethanolamide

AbstractThe surface activities and application properties of aqueous solution surfactants are greatly influenced by their structure, especially the spacer group that connects the polar head groups. Herein, four new non‐ionic Gemini surfactants with different spacers were designed and synthesized, and their surfactant properties and biodegradability were studied. The synthesis of these compounds involves a two‐step procedure. The first step is the formation of an amide from lauric acid and diethanolamine. The second step is the reaction of lauryl diethanolamide with four different spacers, the latter being flexible‐hydrophilic, and rigid‐hydrophobic in structure, respectively. Their structures were characterized using 1H NMR, 13C NMR, FT‐IR, and ESI‐MS. The critical micelle concentration (CMC), the surface tension at CMC (γCMC), the efficiency of these compounds to reduce the surface tension by 20 mN/m (C20 and pC20), the effectiveness (πCMC), the maximum surface excess (Γmax), and the minimum surface area (Amin) were measured at 20, 40, and 50°C. The molecular architecture of the spacers in these compounds strongly influences the thermodynamic parameters, such as the standard change for Gibbs free energy of adsorption (ΔG°ads) and the standard change for Gibbs free energy of micellization (ΔG°mic). The ability of these surfactants to reduce surface tension is particularly good, but their distinguishing characteristic is their high relative propensity to form micellar aggregates. This aggregation ability improves as the hydrophilicity and flexibility of the spacer increase. Finally, in less than 30 days, all non‐ionic Gemini surfactants were determined to be 99% biodegradable in river water.

Regulating interlayer charge transfer in MoS2 via in-situ loading of Pd-metallene to enhance piezo-catalytic degradation efficiency: Contributions of low free energy

Molybdenum disulfide (MoS2) is a promising piezoelectric catalytic material that has garnered considerable research attention. However, its application in the water treatment field is hindered by electron/hole recombination, leading to relatively low piezoelectric efficiency. This study proposes a strategy of establishing interlayer electron bridges by anchoring Palladium metallene (Pd-ene) with ultra-high conductivity and high longitudinal strain response into MoS2, aiming to accelerate carrier migration. The Pd-ene/MoS2-3 catalyst exhibited outstanding piezoelectric catalytic activity, achieving a tetracycline degradation efficiency of 96.51 % and a Cr6+ reduction efficiency of 90.45 % within 30 min. PFM and d33 measurements indicated that the piezoelectric response signal and piezoelectric coefficient were 2.17 times and 6.4 times higher, respectively, compared to pure MoS2. Electrochemical tests revealed that the improved piezoelectric performance is primarily due to enhanced transient piezoelectric current response, reaching 5.9 mA/cm2. The presence of Pd-ene significantly boosts the catalyst’s performance in terms of current density, electrochemically active surface area, and impedance when compared to MoS2 alone. Notably, the theory calculations and quantitative experiments on radicals showed a reduction in the band gap width from 2.62 eV to 1.31 eV, creating favorable conditions for lowering the system’s free energy and facilitating the formation of H2O2. Among them, the free energy of H2O adsorption, dissociation to 2OH*, deprotolation to 2O* and desorption to O2 path decreased by 5.21, 4.96, 2.64 and 4.15 eV, respectively. This study presents an innovative strategy for enhancing the piezocatalytic activity of MoS2 and explores the application of metallene in the field of piezoelectronics.

Iron-Induced vacancy and electronic regulation of nickle phosphides for ampere-level alkaline water/seawater splitting

Rational design of non-precious metal catalysts can accelerate the oxygen evolution reaction (OER) kinetics. Herein, inspired by theoretical analysis, in-situ Fe-doped Ni2P/Ni12P5 with rich P vacancies (Fe-NiPx) is designed and constructed, in which the production of P vacancies is induced by Fe doping. Relevant characterizations confirm that the Fe doping and P vacancies can co-adjust the crystal and electronic structures, thereby optimizing the reconstruction behavior and improving the intrinsic activity of reconstructed-derived Ni(Fe)OOH. As a result, it exhibits excellent OER activity with overpotentials of 256 and 276 mV to achieve the current density of 100 mA cm−2 in 1 M KOH solutions and alkaline seawater, respectively. Furthermore, the Fe-NiPx electrode only requires 1.861 and 1.889 V to drive the 1.0 A cm−2 overall water and seawater splitting, respectively, and maintains stable output as high as 1000 h. Also, to demonstrate the great application potential, green energy-to-hydrogen systems are established. Electrochemical tests and theoretical calculations reveal that reconstructed-Fe-NiPx facilitates the OER kinetics under the adsorbate evolution mechanism (AEM) pathway, with optimized adsorption free energies of intermediates and reduced reaction energy barriers. This work provides new insights into efficient water and seawater splitting through in-situ heteroatom doping and vacancy engineering.

Improved CO2 capture capacity of waste sawmill dust derived activated carbon employing novel high-pressure CO2 activation

The porosity of activated carbon is significantly influenced by both the precursor biomass and the activation parameters. Waste sawmill wood (WSW) dust, an abundantly available precursor from the furniture manufacturing, construction, carpentry, and shipbuilding industries, was collected, dried, pulverized, carbonized, and activated using steam and a novel high-pressure CO2 activation approach. Activation was performed in a tubular furnace at 800 °C with a pure CO2 flow for 90 min at 1 MPa pressure (WSW-A800-CO2-90 min-1 MPa). Another activated carbon sample was synthesized from the same precursor at atmospheric pressure using steam flow at 700 °C for 20 min (WSW-A700-Steam-20 min). XRD and FTIR analyses were conducted to compare the structural information of both samples. Additionally, the thermal characteristics of the samples were determined by measuring their specific heat capacities. N2 and CO2 adsorption experiments were performed to investigate the porous properties and CO2 capture capacities of the synthesized samples. The activated carbon synthesized in a pressurized CO2 environment produced a BET surface area of 684 m2/g, while steam activation achieved a BET surface area of 947 m2/g. Interestingly, despite the lower surface area of the CO2-activated sample, it exhibited a higher CO2 adsorption capacity (106.29 mg/g at 5 °C and 110 kPa) compared to the steam-activated carbon due to its unique pore size distribution. The experimental CO2 adsorption data were also correlated with Langmuir, Freundlich, and modified Dubinin-Astakhov (D-A) models to elucidate the CO2 capture parameters, such as isosteric heat of adsorption, activation energy, and Gibbs free energy.

Electrochemical study and modeling of an innovative pyrazole carboxamide derivative as an inhibitor for carbon steel corrosion in acidic environment.

The impact of N,1-dibenzyl-5-methyl-1H-pyrazol-3-carboxamide (BPC) on the carbon steel (CS) corrosion in hydrochloric acid (1M) was studied in this work, considering concentration and temperature effects. Electrochemical investigation indicated that BPC functions as a mixed-type inhibitor. For an optimal BPC concentration of 125ppm, the inhibition efficiency of 91.55% was obtained at 298K. According to adsorption isotherm of Langmuir, the BPC adheres to the CS with standard adsorption free energy (ΔG°ads) of - 26.76kJmol-1. Furthermore, the calculation of dissolution activation parameters revealed an increase in energy (Ea) from 46.48 to 94.97kJmol-1, an elevation in the enthalpy (∆Ha) from 43.89 to 92.37kJmol-1, and a rise in the entropy (∆Sa) from - 91.17 to 51.43Jmol-1K-1 in the presence of 125ppm of BPC. The experimental results were confirmed by quantum chemistry calculations based on density functional theory (DFT) and molecular simulations using the Monte Carlo method. These theoretical approaches also allowed for a comparison of the inhibitory performances of BPC with its protonated form, BPCH, the latter being found more effective. Moreover, the study of the radial distribution function g(r) predicted that the nature of the bond formed with the steel surface is of a chemical type.

Carob fruit extract as naturally products corrosion inhibitor for copper-nickel alloys in brine solutions

Copper-nickel alloys are the preferred material for desalination facilities and condensers and heat exchangers that use saltwater as a coolant. The eco-friendly compounds especially Carob fruit extract (CFE) has emerged as excessive green corrosion inhibitor for alloys. Cu-Ni alloys are widely used in various industries due to their excellent corrosion resistance. However, their performance can be compromised in aggressive environments like seawater (which is approximately 3.5% NaCl). To evaluate the corrosion behavior of these alloys and the effectiveness of corrosion inhibitors, researchers often employ weight loss, potentiodynamic polarization, and impedance spectroscopy techniques. The results showed that CFE exhibited a good ability to decrease the CR of alloys in 3.5% NaCl solution. The inhibition efficacy (IE) was reached to 92.6% and ̴ 83.2% at 300 ppm dose of CFE for Cu-10Ni alloy and Cu-30Ni alloy, respectively. The CR increases with temperature rising, but the addition of CFE reduces the CR, and the reduction depends on the dose of the extract. Adsorption of the extract gives a good fit to Langmuir, Temkin, and Freundlich isotherms model. The free adsorption energies of CFE on Cu-10Ni and Cu-30Ni alloys were 17.61 and 15.86 kJ mol−1, respectively, suggesting that CFE was weakly held to both alloys. The presence of a protective film on the alloys surface is confirmed by using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and atomic force microscope (AFM). The study suggests that utilizing affordable, natural substances as green corrosion inhibitors presents a new strategy for promoting both resource efficiency and environmental sustainability.

Hydrogen evolution performance of single atom catalyst supported on holey graphdiyne

Abstract Electrocatalytic hydrogen production is an effective method to solve environmental issues and energy crisis. However, cheap and high performance electrocatalysts are still very scarce. In this work, the hydrogen evolution reaction performance of holey graphdiyne supported transition metals single-atom catalysts (TM-SAC-HGY) were investigated by first-principles study. It is found that TM atoms are stably anchored on monolayer HGY by forming TM-C bonds. Meanwhile, TM atoms transfer electrons to both HGY and H atom. More importantly, the H adsorption free energy (ΔGH) of Cu-SAC-HGY is 0.028 eV, which is very close to 0 eV. Therefore, Cu-SAC-HGY has excellent HER activity. By analyzing the results of partial density of states, it can be concluded that the orbital hybridization strength of TM and H plays a decisive role in affecting HER activity. This work could contribute to the development of more efficient HER electrocatalysts.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at −10 mA cm−2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

Biphasic 1T/2H-MoS2 Nanosheets In Situ Vertically Anchored on Reduced Graphene Oxide via Covalent Coupling of the Mo-O-C Bond for Enhanced Electrocatalytic Hydrogen Evolution.

Transition-metal dichalcogenides (TMDs) have recently emerged as promising electrocatalysts for the hydrogen evolution reaction owing to their tunable electronic properties. However, TMDs still encounter inherent limitations, including insufficient active sites, poor conductivity, and instability; thus, their performance breakthrough mainly depends on structural optimization in hybridization with a conductive matrix and phase modulation. Herein, a 1T/2H-MoS2/rGO hybrid was rationally fabricated, which is characterized by biphasic 1T/2H-MoS2 nanosheets in situ vertically anchored on reduced graphene oxide (rGO) with strong C-O-Mo covalent coupling. The rGO substrate improves the conductivity and ensures high-dispersed 1T/2H-MoS2 nanosheets to expose plentiful highly active edges. More importantly, the strong heterointerface electrical interaction by the C-O-Mo covalent bond can enhance the charge-transfer efficiency and reinforce structural stability. Furthermore, the integration with the appropriate 2H phase is in favor of stabilization of the metastable 1T phase; thus, the ratio of 1T and 2H was precisely regulated to balance activity and stability. With these advantages, the 1T/2H-MoS2/rGO catalyst presents a satisfactory activity and stability, as confirmed by the relatively low overpotential (268 and 140 mV at 10 mA cm-2) and the small Tafel slope (102 and 86 mV dec-1) in alkaline and acidic media, respectively. The theory calculations disclose that the electronic structure redistribution has been optimized via the strong coupled C-O-Mo heterointerface and phase interface, significantly reducing the adsorption free energy of hydrogen and improving intrinsic activity.

New Advances on the Dispersive and Polar Surface Properties of Poly(styrene-co-butadiene) Using Inverse Gas Chromatography.

The IGC surface technique led to the dispersive and polar properties of poly(styrene-co-butadiene) rubber (SBR) by adsorption of organic solvents at various temperatures. Our new methodology, based on the thermal Hamieh model and the London dispersion interaction energy, was used to determine the London dispersion surface energy, the polar acid-base surface energy, and the Lewis acid-base properties of the copolymer. The different surface energy parameters of the SBR were obtained as a function of temperature from the chromatographic measurements. The dispersive and polar free energies of adsorption of the various n-alkanes and polar molecules on poly(styrene-co-butadiene) were determined at different temperatures. A decrease in the London dispersive surface energy and the polar Lewis acid-base surface energies of SBR was highlighted when the temperature increased. It showed a Lewis amphoteric character of poly(styrene-co-butadiene) with a highest basic constant 10 times larger than its acidic constant. This new and original method can better characterize the surface thermodynamic properties of poly(styrene-co-butadiene).

Eco-friendly impact of a novel green Melilotus officinalis extract as a sustainable inhibitor to reduce acid corrosion of copper.

In this study, we deployed green Melilotus officinalis extract (MOE) as a corrosion inhibitor for copper. The anticorrosion properties of MOE for Cu in 1 M HNO3 were investigated by various experimental and numerical techniques, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and a weight loss (WL) method at different temperatures. Additionally, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX) and atomic force microscopy (AFM) were utilized to examine the surface morphology of Cu with and without the extract. By contrasting the inhibition effectiveness with and without the extract, the inhibition efficiency (% IE) was observed. The WL method revealed that 300 ppm of the extract had an IE of 93.8% for Cu immersed in one molar HNO3 solution. The MOE was classified as a mixed type according to the PDP study since it delayed both cathodic and anodic processes, with a cathodic predominance. At 25-45 °C, MOE's free adsorption energies were 23.1-21.5 kJ mol-1, showing that mixed-type adsorption occurred on the Cu surface. Additionally, the Langmuir adsorption isotherm and the adsorption data from the WL tests of MOE showed a good match. The extract could adsorb spontaneously onto the metal surface, according to the thermodynamic conditions. Analysis of the corrosion product using different techniques revealed that a protective layer had formed on the metal's surface. Hence, MOE had a good corrosive inhibitive effect on Cu in HNO3 solution. It turned out that all the methods used gave consistent results.

Atomic Hydrogen Interaction with Transition Metal Surfaces: A High-Throughput Computational Study.

Hydrogen adatoms are involved in many reactions catalyzed by Transition Metal (TM) surfaces, such as the Haber-Bosch process or the reverse water gas shift reaction, key to our modern society. Any rational improvement on such a catalyst requires an atomistic knowledge of the metal↔hydrogen interaction, only attainable from first-principles calculations on suited, realistic models. The present thorough density functional theory study evaluates such H interaction at a low coverage on most stable surfaces of bcc, fcc, and hcp TMs. These are (001), (011), and (111) for bcc and fcc TMs and (0001), (101̅0), and (112̅0) for hcp, covering 27 TMs and 81 different TM surfaces in total. In general terms, the results validate, while expanding, previous assessments, revealing that TM surfaces can be divided into two main groups, one in the majority where H2 would be thermodynamically driven to dissociate into H adatoms, located at heights of ∼0.5 or ∼1.0 Å, and another for late TMs, generally with a d 10 electronic configuration, where H2 adsorption with no dissociation would be preferred. No trends in H adsorption energies are found down the groups, but yes along the d series, with a best linear adjustment found for the d-band center descriptor, especially suited for close-packed fcc and hcp TMs surfaces, with a mean absolute error of 0.15 eV. Gibbs free adsorption energies reveal a theoretical volcano plot where fcc TMs are best suited, but with peak Pt performance displaced due to dispersive force inclusion in the method. Still, the volcano plot with respect to the experimental logarithm of the exchanged current density polycrystalline data is far from being valid for a quantitative assessment, although useful for a qualitative screening and to confirm the trends computationally observed.

Evaluation of mixed micellization behavior of imipramine hydrochloride drug and an ionic liquid mixture using different techniques: Effect of urea solutions

Micellization and interfacial behaviors of an ionic liquid 1-hexadecyl-3-methylimidazolium chloride (HMICL-16) mixed with a drug imipramine hydrochloride (IMH) were investigated in aqueous and aquo-urea (250 and 500 mmol kg−1) solutions using tensiometry as a probe. The drastic decline in the critical micelle concentration (cmc) of the mixed system confirms strong interaction supported by the energetic parameters in the mixed micelle and mixed surface in aqueous and aquo-urea media. Density Functional Theory (DFT) has been employed for the optimization of the geometrical structures of the ionic liquid and the drug moieties as well as of their coordinated structures to quantify the interactions in the mixed system through the Frontier Molecular Orbital (FMO) approach. Urea remarkably influences hydrogen bonding conformation of the hydrophobic region by changing the dielectric constant of water. As compared to aqueous system, non-ideality in IMH + HMICL-16 in aquo-urea solvent (250 mmol kg−1) was found to be reduced and the extent of nonideality further decreases with increase in [urea] to 500 mmol kg−1. Using surface tension method different physio-chemical parameters (interaction parameter, composition of components, activity coefficient, thermodynamic parameters, etc.) have been determined and interpreted. Both micellization and adsorption of IHM are found to be spontaneous in all the media investigated as indicated by the negative values of the free energies of micellization (−17.82, −17.66, and −17.57 kJ mol−1 respectively in water, 250 mmol kg−1 urea, and 500 mmol kg−1 urea), and the free energies of adsorption (−40.06, −39.30, and −32.92 kJ mol−1 respectively in these media). The addition of HMICL-16 to IMH causes an increased spontaneity of both the micellization and adsorption processes. FTIR and UV–visible spectral techniques were employed to assess the interactions amongst IMH and HMICL-16. UV–visible study of IMH shows maximum absorption at a wavelength of 249 nm due to a π-π∗ transition which underwent a hyperchromic shift upon interaction with HMICL-16. A quantitative estimation based on the Benesi-Hildebrand equation demonstrates negative values of free energy (ΔG) confirming the formation of energetically favorable complex in the investigated systems.

Self-Reconstructed Amorphous CoOx/NiCoB Heterostructure Catalysts for Enhanced HER Performance.

Amorphous electrocatalysts exhibit potentials as precursors for triggering the in situ reconstruction to generate the real catalytic active species toward electrochemical processes. In this work, a new kind of amorphous Ni-Co-B alloy pre-catalysts for hydrogen evolution reaction (HER) is reported, which is obtained via a facile electroless plating strategy on the nickel foam (NF). Interestingly, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and morphological characterizations identify the in situ reconstruction process during HER accompanied by the preferential leaching of surface B species and the formation of amorphous CoOx nanosheet arrays as the real active sites. Benefiting from the synergistic effect between the surface CoOx layer and the inner unaltered NiCoB phase, the resultant CoOx/NiCoB heterostructure catalyst achieves a low overpotential of 209mV at the elevated current density of 500mA cm-2 and maintains stability for 300h without significant attenuation. Theoretical calculation reveals the electron reconfiguration at the interfaces between the newly formed CoOx and inner NiCoB phases, which is favorable for the stabilization of reconstructed active oxide layers at the reductive potentials for catalyzing HER. Moreover, the CoOx/NiCoB heterostructure optimizes hydrogen adsorption free energies, thereby enhancing HER catalytic activity.

Experimental and advanced equilibrium studies on the enhanced adsorption of phosphate, cadmium, and safranin dye pollutants using methoxy exfoliated glauconite.

Natural glauconite, as a mixed-layered clay mineral, was subjected to exfoliation processes, producing silicate monolayers or individual sheets that were further modified with methanol into methoxy exfoliated glauconite (Mth/EXG). The structure was assessed as an enhanced adsorbent for three types of common water contaminants, including phosphate (PO4 3-), safranin-O dye (SFR), and cadmium metal ions (Cd2+). The Mth/EXG structure achieved promising adsorption capacities at the saturation points equal to 269.9mg/g for PO4 3-, 312mg/g for SFR, and 234.5mg/g for Cd2+ which are significantly better than the reported values for several studied adsorbents of higher costs and complex production procedures. The adsorption processes and the predicted regulated mechanisms in terms of the adsorbate/adsorbent interface were illustrated based on the steric and energetic findings that correspond to the applied monolayer equilibrium model of one energy site. The structure displays active site densities of 82.5mg/g (PO4 3-), 136.3mg/g (SFR), and 83.4mg/g (Cd2+), which illustrate the high uptake performance of SFR. Also, the steric parameters reflected the suitability of each existing site to be filled with 4 ions of PO4 3-, SFR, and Cd2+. The adsorption energy (less than 40kJ/mol) in conjunction with free adsorption energy from D-R model (8-16kJ/mol) and steric parameters validate the dominant impact of the multi-ionic physical mechanisms (hydrogen bonding and van der Waals forces), in addition to the assistant impact of some weak chemical processes that might be assigned to the formed inner-sphere complex. Also, these reactions all occurred spontaneously with exothermic behaviors according to the thermodynamic functions. Additionally, the structure exhibit significant affinity for the studied pollutants even in the existing of completive chemical including anions, cations and organic molecules.

Adsorption mechanism study of viscoelastic surfactants with various molecular structures on oil and gas reservoir rocks

As clean thickeners used in fracturing fluids or self-diverting acids, viscoelastic surfactants (VESs) have garnered increased attention for their unique properties. While VESs leave little residue, their adsorption on rocks can lead to adverse effects on oil and gas seepage. Herein, sandstone and limestone were utilized as adsorbents to examine a series of VESs with diverse molecular structures. The relationship between adsorption capacity and molecular structure was investigated, along with the impact of salinity and temperature on adsorption capacity through static and dynamic adsorption tests. Experiments were conducted at various temperatures (25 °C–100 °C) and different salinity levels (0–4 wt%) using sandstone and limestone as adsorbents. The wettability alteration caused by each VES solution was assessed to confirm the adsorption capacity of these VESs on sandstone and limestone. Scanning electron microscopy was employed to visually study the microscopic morphologies of rock surfaces after adsorption in VES solutions to investigate the adsorption characteristics. Owing to the differing charges between sandstone and limestone, the adsorption capacity of each VES varied. Cationic VESs tend to be absorbed by sandstone, while zwitterionic VESs are easily adsorbed by limestone. The increase in salinity considerably enhances the adsorption capacity of rocks, with a greater amplification on sandstone compared to limestone. Additionally, the adsorption capacity of cationic VESs on sandstone is highly sensitive to salinity owing to the ease with which their head groups are disrupted by ions. Rising temperatures can weaken adsorption capacity due to the breakdown of hydrogen bonding or van der Waals forces. The wettability changes caused by VES solutions on sandstone are more pronounced than on limestone. By combining experimental results, the mineral content of rocks, molecular structure characteristics of VESs, and adsorption-free energy, the adsorption mechanisms of various VESs with different molecular structures on rocks were examined. This research lays a theoretical foundation for optimizing VES molecular structures for the preparation of fracturing fluids or self-diverting acid.

Breaking the linear scaling relationship in BN-supported metal catalysts for efficient CO2RR towards C1 and C2 products

The catalytic activity and selectivity of CO2 reduction reaction (CO2RR) towards C1 and C2 products are fundamentally restricted by the inherent linear scaling relationship among the adsorption-free energies of intermediates. To face this challenge, we have proposed a novel multifunctional M1M2@BN electrocatalysts to break the linear scaling relationships in CO2RR and efficiently obtain C1 and C2 products. Our results reveal that the optimal limiting potential is increased from −0.58 V for M@BN to −0.39 V for M1M2@BN, which achieves ultrahigh activity of CO2RR. Further mechanism analysis illuminates that M1M2@BN can selectivity modulate the adsorption strength of OCHO* and OCH2O*/OCHOH*, breaking the linear scaling relationship of adsorption-free energies of key intermediates to achieve the enhanced catalytic activity. Notably, the sufficient active sites on M1M2@BN electrocatalysts can promote the sluggish C–C coupling by capturing two CO intermediates simultaneously, further generating high-value multi-carbon (CH2CH2OH) products. Meanwhile, the thermodynamic stability of M1M2@BN has been demonstrated by ab initio molecular dynamics (AIMD) simulations, which shows the feasibility of commercial application in CO2RR. Our findings provide a novel strategy to modulate the binding strength of intermediates and develop the design of efficient multi-active-site CO2RR electrocatalysts.

Active Site Customizing of Metal-Organic Materials for Highly Efficient Oxygen Evolution.

Elucidating the correlation of active sites and catalytic activity in multi-component metal-organic frameworks (MOFs) is key to understanding the mechanism of oxygen evolution reaction (OER), yet it remains nebulous. Herein, a direct pathway combining theoretical prediction with anchoring high-valence metals is proposed on MOFs to reveal the mechanism of the OER reaction. Density functional theory (DFT) predicts that the co-modulation by Mo and Co atoms can enhance the conductance of CoMOF and optimize the adsorption-free energies of the OER intermediates. Guided by the theoretical prediction, the Co-based MOFs grown on Ni foams are doped with high valence Mo, which is used as model catalysts for the quantitative study of the composition-dependent OER performance. With Co/Mo in the ratio of 5:1 for the highest OER activity (impressively overpotential of 324mV at 100mA cm-2 and a Tafel slope of 96.07mV dec-1) and excellent stability (maintains for 200h at 100mA cm-2), the catalysts in this work is superior to commercial benchmarks electrocatalysts (RuO2/NF, 420mV, 199.12mV dec-1). This work sheds light on the tailoring of the active sites of MOFs, which is highly correlated with the activity of the OER.