Pore Confinement Effect Research Articles

Polymerization-Induced Aggregation Approach toward Uniform Pd Nanoparticle-Decorated Mesoporous SiO2/WO3 Microspheres for Hydrogen Sensing

Hydrogen as an important clean energy source with a high energy density has attracted extensive attention in fuel cell vehicles and industrial production. However, considering its flammable and explosive property, gas sensors are desperately desired to efficiently monitor H2 concentration in practical applications. Herein, a facile polymerization-induced aggregation strategy was proposed to synthesize uniform Si-doped mesoporous WO3 (Si-mWO3) microspheres with tunable sizes. The polymerization of the melamine-formaldehyde resin prepolymer (MF prepolymer) in the presence of silicotungstic acid hydrate (abbreviated as H4SiW) leads to uniform MF/H4SiW hybrid microspheres, which can be converted into Si-mWO3 microspheres through a simple thermal decomposition treatment process. In addition, benefiting from the pore confinement effect, monodispersed Pd-decorated Si-mWO3 microspheres (Pd/Si-mWO3) were subsequently synthesized and applied as sensitive materials for the sensing and detection of hydrogen. Owing to the oxygen spillover effect of Pd nanoparticles, Pd/Si-mWO3 enables adsorption of more oxygen anions than pure mWO3. These Pd nanoparticles dispersed on the surface of Si-mWO3 accelerated the dissociation of hydrogen and promoted charge transfer between Pd nanoparticles and WO3 crystal particles, which enhanced the sensing sensitivity toward H2. As a result, the gas sensor based on Pd/Si-mWO3 microspheres exhibited excellent selectivity and sensitivity (Rair/Rgas = 33.5) to 50 ppm H2 at a relatively low operating temperature (210 °C), which was 30 times higher than that of the pure Si-mWO3 sensor. To develop intelligent sensors, a portable sensor module based on Pd/Si-mWO3 in combination with wireless Bluetooth connection was designed, which achieved real-time monitoring of H2 concentration, opening up the possibility for use as intelligent H2 sensors.

Electron-rich platinum single sites anchored on sulfur-doped covalent organic frameworks for boosting anti-Markovnikov hydrosilylation of alkenes

Selective catalytic hydrosilylation of alkenes for the synthesis of organosilicon products is very important in the fine chemical industry. Nevertheless, conventional Pt-based homogeneous catalysts are hindered by their low reaction selectivity, catalyst residues, and Pt leaching. In this study, a series of covalent organic frameworks (COFs)-anchored single-site Pt catalysts for achieving high-performance alkene hydrosilylation were prepared, and comprehensive characterizations confirmed that the actual coordination environment of Pt active sites is NS-Pt-Cl2. The resulting Pt(0.75%)@BTT-BPh-COF catalyst exhibited superior activity for the anti-Markovnikov hydrosilylation of alkenes with an excellent selectivity (>99%) under solvent-free conditions. Experimental and theoretical analysis revealed that the excellent catalytic performance is attributed to the effective charge transfer and strong coordination effect between Pt and S, N-co-doped COFs, which is conducive to the generation of electron-rich and highly active Pt single sites. High catalyst stability was maintained during recycling experiments due to the strong anchoring effect of the COFs support on atomically dispersed Pt single sites as well as the pore confinement effect. This study not only describes the precise design for the state-of-the-art catalysts with accurate active sites but also affords in-depth insights into alkene hydrosilylation.

Optimization of CO2 Huff-n-Puff in Unconventional Reservoirs with a Focus on Pore Confinement Effects, Fluid Types, and Completion Parameters

The cyclic injection of CO2, referred to as the huff-n-puff (HnP) method, is an attractive option to improve oil recovery from unconventional reservoirs. This study evaluates the optimization of the CO2 HnP method and provides insight into the aspects of CO2 sequestration for unconventional reservoirs. Furthermore, this study also examines the impact of nanopore confinement, fluid composition, injection solvent, diffusivity parameters, and fracture properties on the long-term recovery factor. The results from over 500 independent simulations showed that the optimal recovery is obtained for the puff-to-huff ratio of around 2.73 with a soak period of fewer than 2.7 days. After numerous HnP cycles, an optimized CO2 HnP process resulted in about 970-to-1067-ton CO2 storage per fracture and over 32% recovery, compared to 22% recovery for natural depletion over the 30 years. The optimized CO2 HnP process also showed higher effectiveness compared to the N2 HnP scenario. Additionally, for reservoirs with significant pore confinement (pore size ≤ 10 nm), the oil recovery improved by over 3% compared to the unconfined bulk phase properties. We also observed over 300% improvement in recovery factor for a fluid with a significant fraction of light hydrocarbons (C1–C6), compared to just a 50% improvement in recovery for a fluid with a substantial fraction of heavy hydrocarbons (C7+). Finally, the results also showed that fracture properties are much more important for CO2 HnP than natural depletion. This study provides critical insights to optimize and improve CO2 HnP operations for different fluid phases and fracture properties encountered in unconventional reservoirs.

Three-dimensional ordered microporous silica supported p-lanthanum ferrite and n-ceria as heterojunction photocatalyst to activate peroxymonosulfate for bisphenol a degradation

In this study, three-dimensional ordered microporous silica supported p-lanthanum ferrite and n-ceria (n-CeO2@p-LaFeO3/3DOM SiO2) was successfully synthesized as a visible light-driven photocatalyst for activating peroxymonosulfate (PMS) to degrade Bisphenol A (BPA). In a wide pH range (2–12), the BPA degradation efficiency maintained at a high level, organic matter and natural inorganic ions had no significant negative impact. When the BPA concentration was as low as 2 mg·L−1, the removal rate in 60 min still reached 95.56%, indicating that the novel photocatalyst has potential application in the treatment of trace pollutants. The pore confinement effects of catalysts and the synergistic effect between LaFeO3 and CeO2 result in the excellent photocatalytic performance. We proposed the possible mechanism of BPA degradation, specifically involving the recognition and generation mechanism of reactive oxygen species (ROSs), adsorption processes and diffusion processes. In summary, the novel n-CeO2@p-LaFeO3/3DOM SiO2 would be a promising candidate photocatalytic material for practical sewage treatment.

Unveiling a remarkable enhancement role by designing a confined structure Ho-TNTs@Mn catalyst for low-temperature NH3-SCR reaction.

MnOx-based catalysts are considered promising alternative catalysts for NH3-SCR to remove NOx at low temperature. However, their poor SO2 or H2O tolerance and unfavorable N2 selectivity are still the main obstacles restraining their further practical application. Herein, we carefully confined the manganese oxide active species in Ho-modified titanium nanotubes to improve their SO2 resistance and N2 selectivity. Ho-TNTs@Mn exhibits excellent catalytic activity, strong SO2 and H2O tolerance and superior N2 selectivity, and more than 80% NO conversion can be achieved in the range 80-300 °C with 100% N2 selectivity. The characterization results verify that the pore confinement effect of Ho-TNTs for Mn increases the dispersion of Mn to promote the interfacial effect between Mn and Ho. The electron synergistic effect between Mn and Ho improves the electron transformation of Mn and Ho, which inhibits electron transfer between SO2 and Mn to avoid poisoning from SO2. We also find that the interaction between Ho and Mn induces electron migration to restrain the production of Mn4+, contributing to the suitable redox capacity to decrease the creation of byproducts, which serves as the motivation for high N2 selectivity. In situ DRIFTs analysis clarifies that Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms co-exist in the NH3-SCR reaction over Ho-TNTs@Mn, and the E-R reaction mechanism predominates We believe that Ho-TNTs@Mn with a well-designed nanotube structure will show preferable development and application prospects in the NH3-SCR reaction.

Incorporating quaternary mesoporous nanospheres and DNA stochastic nanowalkers into a signal amplified switch: A highly sensitive electrochemical assay for APE1

In this work, we engineered a quaternary mesoporous nanosphere by boron- and phosphorus-codoped Pd-Pt alloy ([email protected]@Pt) to prepare a DNA stochastic nanowalker for catalysis efficiency and local concentration enhancement, which can be applied as an excellent signal amplified switch to electrochemically detect apurinic endonuclease 1 (APE1) with the assist of a highly efficient proximity ligation assay (PLA)-based protein conversion strategy. Specifically, the synthetic [email protected]@Pt nanomaterial showed excellent catalytic performance for electroactive substances (ferrocene) due to the desirable pore confinement effect and abundant active sites. Moreover, it can be employed to program a DNA stochastic nanowalker to significantly improve the detection sensitivity and response time. In addition, by designing a highly efficient PLA-based protein converting strategy, the target APE1 can be efficiently recognized to concurrently convert APE1 to enormous DNA outputs, which promoted the detection selectivity and sensitivity for APE1 in the range of 1 fg/mL to 1 pg/mL with a detection limit of 0.45 fg/mL. Although the [email protected]@Pt-based DNA stochastic nanowalker driven by the biological enzyme whose activity may be affected by the environment, the as-prepared electrochemical biosensor based on the [email protected]@Pt-based DNA stochastic nanowalker has still achieved good detection performance, and possesses enormous potential for the applications of new-type DNA nanomachines in biosensing, bioimaging and clinical diagnosis.

Improving Photocatalytic Stille Coupling Reaction by CuPd Alloy-Doped Ordered Mesoporous TiO2

Rational surface engineering of noble metal-doped photocatalysts is essential for the efficient conversion of solar energy into chemical energy, but it is still challenging to perform. Herein, we reported an effective strategy for structuring alloyed CuPd (CP) nanoclusters on the ordered mesoporous TiO2 (CPT) by a pore confinement effect. The resultant CPT exhibited an extraordinary photocatalytic activity during Stille reaction under visible light. The X-ray photoelectron spectroscopy spectra, the field emission scanning electron microscope (FESEM) images, and the aberration-corrected high-angle annular dark scanning transmission electron microscopy (HAADF-STEM) images demonstrated that CP nanoclusters were anchored in the mesoporous pore wall of TiO2, and the atomic ratio as well as densities of CP could be precisely modulated via the coordination configuration. As the atomic ratio of CP to TiO2 increased to a certain extent, their photocatalytic activity during Stille reaction increased. A mechanistic investigation suggested that the CP alloy could absorb visible light and its conduction electrons gained energy, which were available at the surface Pd sites. This allowed the Pd sites to become electron-rich and to accelerate the rate-determining step of the Stille reaction. As a result, the efficiency of the photocatalytic Stille coupling reaction was extraordinary enhanced.

Investigation of shale gas flows under confinement using a self-consistent multiscale approach

This report summarises our recent findings on non-ideal gas flow characteristics in shale nanopores facilitated by our strongly-inhomogeneous kinetic model. As there are a significant portion of nano-scale pores in shale, gas molecule size is comparable to both the gas mean free path and the characteristic length of the flow domain, and various factors including fluid-solid and fluid-fluid interactions, pore confinement, surface roughness, and non-equilibrium effect need to be considered in a self-consistent manner. These factors are either considered in the governing equation according to the dense gas and mean-field theories, or through the boundary condition based on molecular dynamics simulations. Our kinetic model results are consistent with the molecular dynamics data at the molecular scale and converge to the continuum predictions when pores become large. This model serves as an accurate tool to investigate multiscale transport of shale gas and is helpful for upscaling from the microscopic to continuum levels with a firm theoretical basis. Cited as: Shan, B., Ju, L., Guo, Z., Zhang, Y. Investigation of shale gas flows under confinement using a self-consistent multiscale approach. Advances in Geo-Energy Research, 2022, 6(6): 537-538 . https://doi.org/10.46690/ager.2022.06.11

Understanding the role of support structure in methane dry reforming for syngas production

Dry reforming of methane (DRM) is an efficient reaction path in converting two major greenhouse gases of CO2 and CH4 into valuable chemical products. However, the rapid deactivation of catalysts restricts its development to a large extent. Attempts to combat the problem have been made in this work through evaluating potential supports of La0.7Sr0.3AlO3 and SBA-15, and understanding the confinement effect of support pores, in order to construct Ni-catalysts with high activity and durability. Results show that SBA-15 support possesses better resistance to carbon deposition than La0.7Sr0.3AlO3, leading to a much better catalytic performance in DRM. Moreover, Ni/SBA-15 catalyst with pores smaller than approximate 10 nm is found to be able to withstand very harsh DRM reaction conditions of GHSV = 72,000 mLgcat−1h−1and CH4/CO2 = 1.5 for 10 h at 650 °C, and the stability of catalysts is determined to be in the order of Ni/SBA-15 > Ni/SBA-15-HC > Ni/SBA-15-TMB. The reason is suggested to be the mitigation of nickel particles aggregation due to confining pores.

High efficiency electrochemiluminescence of 3D porous g-C3N4 with dissolved O2 as co-reactant and its sensing application for ultrasensitive detection of microRNA in tumor cells

In this work, the electrochemiluminescence (ECL) phenomenon of three-dimensional graphitic carbon nitride (3D g-C3N4) was reported. Firstly, the proposed 3D g-C3N4 possessed 3D porous interconnected open-framework which enabled faster charge transport and efficient penetration of co-reactants due to “pore confinement effect”. Then, we found that the dissolved O2 could serve as an excellent co-reactant for cathodic ECL of 3D g-C3N4. And the high specific surface area was beneficial to better adsorbing and gathering of dissolved O2 and reactive oxygen species (ROSs), which made them full contact on the surface or inside of 3D g-C3N4, giving a more sufficient ECL reaction and higher ECL signal. Based on the proposed 3D g-C3N4-O2 ECL system, a sensitive biosensor was constructed for microRNA-21 (miRNA-21) detection with assistance of 3D spherical tracks assisted 3D DNA walking machine, which exhibited superior performance for miRNA-21 with detection limit of 0.22 fM. The proposed 3D g-C3N4-O2 ECL system with high ECL efficiency and the effective target conversion and amplification strategies were beneficial to construct ultra-sensitive ECL sensing platform, which would be better applied to clinical bioanalysis.

Electrochemiluminescence covalent organic framework coupling with CRISPR/Cas12a-mediated biosensor for pesticide residue detection

The trace detection of pesticide residue becomes particularly important since increasing attentions have been attached to food safety. Herein, we developed an electrochemiluminescence (ECL) covalent organic framework (COF) based-biosensor for trace pesticide detection coupling with CRISPR/Cas12a-mediated signal accumulation strategy. Firstly, the target conversion was carried out with an aptamer-assembled magnetic spherical nucleic acids, which can convert acetamiprid to activator DNA, triggering the CRISPR/Cas12a to make quenching probes far away from electrode for signal accumulation. The COF with stable and strong ECL was synthesized by a condensation reaction between the perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and melamine (MA), due to the highly ordered arrangement of the PTCDA luminescence units among COF structure and the pore confinement effect. Moreover, the designed assay method was successfully employed to detect the residual level of acetamiprid in real sample and expected to be widely used in pesticide-related food safety.

A Microporous Hydrogen-Bonded Organic Framework for Efficient Xe/Kr Separation.

Separation of xenon/krypton gas mixtures is one of the valuable but challenging processes in the gas industries due to their close molecular size and similar physical properties. Here, we report a novel ultramicroporous hydrogen-bonded organic framework (termed as HOF-40) constructed from a cyano-based organic building unit of 1,2,4,5-tetrakis(4-cyanophenyl)benzene (TCPB), exhibiting superior separation performance for Xe/Kr mixtures, as clearly demonstrated by dynamic breakthrough curves. GCMC simulation results indicate that the pore confinement effect and abundant accessible binding sites play a synergistic role in this challenging gas separation. Furthermore, this cyano-based HOF displays excellent chemical stability from 12 M HCl to 20 M NaOH aqueous solutions.

Immobilization of Lewis Basic Sites into a Stable Ethane-Selective MOF Enabling One-Step Separation of Ethylene from a Ternary Mixture.

Purification of C2H4 from a ternary C2H2/C2H6/C2H4 mixture by one-step adsorption separation is of prime importance but challenging in the petrochemical industry; however, effective strategies to design high-performance adsorbents are lacking. We herein report for the first time the incorporation of Lewis basic sites into a C2H6-selective MOF, enabling efficient one-step production of polymer-grade C2H4 from ternary mixtures. Introduction of amino groups into highly stable C2H6-selective UiO-67 can not only partition large pores into smaller cagelike pockets to provide suitable pore confinement but also offer additional binding sites to simultaneously enhance C2H2 and C2H6 adsorption capacities over C2H4. The amino-functionalized UiO-67-(NH2)2 thus exhibits exceptionally high C2H2 and C2H6 uptakes as well as benchmark C2H2/C2H4 and C2H6/C2H4 selectivities, surpassing all of the C2H2/C2H6-selective materials reported so far. Theoretical calculations combined with in situ infrared spectroscopy indicate that the synergetic effect of suitable pore confinement and functional surfaces decorated with amino groups provides overall stronger multipoint van der Waals interactions with C2H2 and C2H6 over C2H4. The exceptional performance of UiO-67-(NH2)2 was evidenced by breakthrough experiments for C2H2/C2H6/C2H4 mixtures under dry and wet conditions, providing a remarkable C2H4 productivity of 0.55 mmol g-1 at ambient conditions.

Recent progress on MXenes and MOFs hybrids: Structure, synthetic strategies and catalytic water splitting

The 2D MXenes (carbides, nitrides, carbonitrides) is an emerging class of atomic layered nanomaterials that calls for intensive investigation. The tunable structures, large-surface to volume ratio, high electrical conductivity, rich surface chemistries, hydrophilicity and large redox active sites are some vital features which makes MXenes the suitable catalyst for water splitting. However, MXenes suffers from the key limitation of agglomeration, reduced long term stability and recyclability. The coupling of MXenes with metal organic frameworks (MOFs) is an effective strategy owing to the high surface area, porosity, diverse functionalities, pore-confinement effect, and tunable coordination space of MOFs provides a preferential environment for hosting MXene to prevent its agglomeration. The review aims to showcase the synergistic effects of MXenes and MOFs hybrids by exploiting the inherent features of both frameworks for water splitting application. Herein, the electronic, structural and optical properties of MXenes and MOFs frameworks are elaborated. A detailed discussion on the synthetic strategies of MXenes and MOFs hybrids explains the importance of etching technique. Lastly, variant future challenges have been highlighted to better understand the present research and progression of MXenes and MOFs hybrids.

CDs assembled metal-organic framework: Exogenous coreactant-free biosensing platform with pore confinement-enhanced electrochemiluminescence

Despite the various synthesis approachs to obtain luminous carbon dots (CDs), it is still quite challenging to construct the efficient electrochemiluminescence (ECL) owing to their low ECL reactivity and easy agglomeration. Herein, an efficient and concise ECL system was skillfully constructed by taking advantage of the nitrogen and sulfur co-doped CDs (N,S-CDs) with surfaces rich in hydrazide groups as luminophors to emit intense ECL, and metal-organic framework (MOF) as the matrix to confine CDs in its nanospace. Surprisingly, the proposed CDs assembled MOF (CDs/ZIF-8) enhanced anodic ECL signal up to 250% of pure CDs under the exogenous coreactant-free condition. As a proof of concept, the highly sensitive detection of uric acid (UA) was realized by the constructed ECL platform with a low detection limit of 3.52 nmol/L ranging from 10 nmol/L to 50 µmol/L. This work expanded ideas for the application of pore confinement effect, and provided references for the detection of disease biomarkers of gout and hyperuricemia.

Fine pore engineering in a series of isoreticular metal-organic frameworks for efficient C2H2/CO2 separation

The separation of C2H2/CO2 is not only industrially important for acetylene purification but also scientifically challenging owing to their high similarities in physical properties and molecular sizes. Ultramicroporous metal-organic frameworks (MOFs) can exhibit a pore confinement effect to differentiate gas molecules of similar size. Herein, we report the fine-tuning of pore sizes in sub-nanometer scale on a series of isoreticular MOFs that can realize highly efficient C2H2/CO2 separation. The subtle structural differences lead to remarkable adsorption performances enhancement. Among four MOF analogs, by integrating appropriate pore size and specific binding sites, [Cu(dps)2(SiF6)] (SIFSIX-dps-Cu, SIFSIX = SiF62-, dps = 4.4’-dipyridylsulfide, also termed as NCU-100) exhibits the highest C2H2 uptake capacity and C2H2/CO2 selectivity. At room temperature, the pore space of SIFSIX-dps-Cu significantly inhibits CO2 molecules but takes up a large amount of C2H2 (4.57 mmol g−1), resulting in a high IAST selectivity of 1787 for C2H2/CO2 separation. The multiple host-guest interactions for C2H2 in both inter- and intralayer cavities are further revealed by dispersion-corrected density functional theory and grand canonical Monte Carlo simulations. Dynamic breakthrough experiments show a clean C2H2/CO2 separation with a high C2H2 working capacity of 2.48 mmol g−1.

Rarefied gas transport in heterogeneous shale matrix using a practical apparent permeability model and fuzzy statistical method

A new shale gas transport model is derived to characterize the matrix structural heterogeneity impact on the gas apparent permeability (AP). The developed analytical model is built upon two steps: first, the homogeneous AP model is formulated by assigning the Knudsen-number-parameterized weight coefficients to flow mechanisms based on the analyses of representative rarefied gas transport models; then, the homogeneous model is improved to the heterogeneous model with the help of fuzzy statistical method to assess the structural heterogeneity influences. More specifically, the homogeneous AP model incorporates the multilayer adsorption, surface diffusion, real gas effect, and pore confinement effect. The physical terms in the apparent permeability including the rarefaction coefficient and multilayer adsorption model are simplified to facilitate the large-scale simulation. Meanwhile, the heterogeneous AP model is quantified by the distribution of porosity, tortuosity, and pore size. It is demonstrated that the developed AP model can reproduce the experimental and numerical experiments for five types of gases. It is concluded that the rarefaction in nanopores could be reasonably characterized by the weighted Knudsen diffusion and viscous flow mechanisms. Moreover, it is noticed that the surface diffusion and Knudsen diffusion cannot be ignored in nanopores with radius smaller than 3 nm at low reservoir pressures. In contrast, the viscous flow plays a significant role in shale gas transport in nanopores with radius larger than 75 nm. In addition, the fuzzy statistical method in the proposed heterogenous model provides the indicators to evaluate the impact of structural heterogeneity on the AP. It is observed that the heterogeneous model can accurately predict the realistic apparent permeability as the heterogeneity increases to σ = 0.15. However, the accuracy decreases when the matrix heterogeneity increases.

Advances in molecular dynamics simulation on heterogeneous nucleation of gas hydrate

Gas hydrate is a nonstoichiometric crystalline material. It is attracting more and more attention not only because natural gas hydrate is a potential energy resource, but also because hydrate-based technologies can be potentially applied to the industry of energy and environment such as energy storage, carbon sequestration, etc. The nucleation mechanism of gas hydrate is a key issue in studying reservoir formation of natural gas hydrate and the kinetic properties of gas hydrate as an energy-storage media. Molecular dynamics simulation can provide microscopic insights into molecular-scale understanding of hydrate nucleation. In this review, the advances on the study of heterogeneous hydrate nucleation by molecular dynamics simulation are summarized, with a specific focus on the factors affecting nucleation processes. The interfacial energy barrier for nucleation will be lowered by molecular structure of interfacial water between hydrate and solid substrate. The interface and surface properties of solid substrate, including hydrophilicity and hydrophobicity, surface roughness, layer-accumulated adsorption potential, crystallinity and surface layer-charge are also recognized as being associated with the process of hydrate nucleation by influencing the dynamics of gas and water molecules. In case of hydrate nucleation in confined pore space, confinement effect, pore size and elasticity are identified as the controlling factors.

Confinement of ultrasmall Pd nanoparticles by layered covalent triazine frameworks for semihydrogenation of acetylene

Acetylene hydrogenation is an important reaction in the petrochemical industry, the key is to develop efficient and selective catalyst. In this work, a highly crystalline layered covalent triazine frameworks (CTFs) with excellent thermal stability was used as carbon support to immobilize ultrasmall Pd nanoparticle for semihydrogenation of acetylene. Downsizing the particle sizes were realized by dual-solution assisted precursor mixture and using H2 instead of NaBH4 as reducing agent.The pore confinement effect of CTFs and the electronic intercalation from N atoms play key roles in improving the catalytic activity and stabilizing the Pd nanoparticles. The Pd/CTFs-H2 catalyst exhibits 100% acetylene conversion and 99.9% ethylene selectivity at 250 °C and space velocity of 110,000 h−1. The life test (>150 h), cycle test and chemical stability test demonstrated the long-term stability of the Pd/CTFs-H2. The process mechanism of selective hydrogenation of acetylene in this catalyst is investigated by the in-situ infrared spectra.

Interfacial Conductivity Enhancement and Pore Confinement Conductivity-Lowering Behavior inside the Nanopores of Solid Silica-gel Nanocomposite Electrolytes.

Solid nanocomposite electrolytes (nano-SCEs) that exhibit higher ionic conductivity than the individual confined electrolyte were investigated for high-performance solid-state batteries. Understanding the behavior of Li-ion conduction through the pores is important to design ideal nanoporous structures for nano-SCEs, which are composed of an ionic liquid electrolyte (ILE) in a highly porous (∼90%) silica matrix. To establish the relationship between the pore structure of the silica matrix and the ionic conductivity of the solid nanocomposite, the liquid electrolyte fraction was successfully extracted from the nano-SCE to reveal the fragile porous silica matrix. A careful drying using the CO2 supercritical drying method helps in sustaining the original structure, preventing its collapse due to surface tension. The pore size distribution, Brunauer-Emmett-Teller (BET) surface area, and porosity were characterized using scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption techniques. Our results revealed a wide size distribution of macropores and mesopores in the silica matrix. The pore size increased and the effective surface area decreased with increasing ILE/SiO2 molar ratio. The interface conductivity enhancement was found to increase with the thickness of the adsorbed (ice-like) bound-water layer on the silica surface, confirming that the strong hydrogen bonding of the adsorbed ionic liquid molecules on the bound-water layer causes the conduction promotion effect in the nano-SCE. In addition, a large number of small pores lead to a severe pore confinement effect that results in a decreased conductivity due to the increasing viscosity of the ILE filling the pores. The conductivity can be improved by realizing a nano-SCE with an optimized pore size to minimize the pore confinement effect.