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[Display omitted] Carbon dioxide (CO 2) reduction is an urgent challenge worldwide due to the dramatically increased CO 2 concentration and concomitant environmental problems. Geological CO 2 storage in gas hydrate in marine sediment is a promising and attractive way to mitigate CO 2 emissions owning to its huge storage capability and safety. However, the sluggish kinetics and unclear enhancing mechanisms of CO 2 hydrate formation limit the practical application of hydrate-based CO 2 storage technologies. Here, we used vermiculite nanoflakes (VMNs) and methionine (Met) to investigate the synergistic promotion of natural clay surface and organic matter on CO 2 hydrate formation kinetics. Induction time and t 90 in VMNs dispersion with Met were shorter by one to two orders of magnitude than Met solution and VMNs dispersion. Besides, CO 2 hydrate formation kinetics showed significant concentration-dependence on both Met and VMNs. The side chains of Met can promote CO 2 hydrate formation by inducing water molecules to form a clathrate-like structure. However, when Met concentration exceeded 3.0 mg/mL, the critical amount of ammonium ions from dissociated Met distorted the ordered structure of water molecules, inhibiting CO 2 hydrate formation. Negatively charged VMNs can attenuate this inhibition by adsorbing ammonium ions in VMNs dispersion. This work sheds light on the formation mechanism of CO 2 hydrate in the presence of clay and organic matter which are the indispensable constituents of marine sediments, also contributes to the practical application of hydrate-based CO 2 storage technologies. [ABSTRACT FROM AUTHOR]

The excellent motion performance of gallium-based liquid metals (LMs) upon the application of a modest electric field has provided a new opportunity for the development of autonomous soft robots. However, the locomotion of LMs often appears in an alkaline solution, which hampers the application under other different conditions. In this work, a novel robot arm is designed to transfer the motion of the LM from an alkaline solution in a synchronous drive mode. The liquid metal droplet (LMD) at the bottom of the robot arm is actuated using a DC voltage to provide the driving force for the system. By introducing an end effector at the center of the robot arm, the synchronous motion of the system is replicated and can be applied to different situations. The theoretical understanding of continuous electrowetting (CEW) at the LM interface is explained, and then the motion performance of the robot arm against the function of the applied voltage and driving direction is investigated. Moreover, several applications using this robot arm, such as pattern drawing, cargo transportation, and drug concentration detection, are demonstrated. The presented robot arm has the potential to observably expand the application fields of the LM. [ABSTRACT FROM AUTHOR]

• V-aerogels can be easily fabricated on a large scale by ion-induced fast gelation. • V-aerogels show excellent thermal insulation and infrared stealth performance. • The V-aerogels demonstrate robust structural stability up to 1300 °C. Low thermal conductivities and high fire resistance are highly desired for the materials used in energy-efficient buildings with high-level safety. Traditional inorganic insulating materials are either fragile or have high thermal conductivities, while organic insulating materials or hybrids with inorganic ones are limited by poor fire resistance and significant volume shrinkage after heating. Herein we report mechanically robust vermiculite aerogels with a thermal conductivity as low as 0.033 W/(m·K), excellent fire resistance, and robust structural stability at high temperatures. The aerogels were assembled from delaminated two-dimensional vermiculite nanosheets via trivalent cations, such as Al3+, Fe3+, and La3+, induced fast gelation. The nanosheet concentration and ion cross-linking play critical roles in forming monolithic and robust aerogels. The vermiculite aerogels can resist a high-temperature flame without disintegration and show almost no volume shrinkage after long-time heat treatment at 700 °C. The excellent robustness and super-insulating performance (0.021 W/(m·K)) remain and even are improved after heating at 900 °C for 1 h. The as-made vermiculite aerogels show low-bulk density, high-porosity, super-insulating performance, excellent fire resistance, and environmental safety, endowing them with great potential as ideal thermal insulators for various applications, such as energy-efficient buildings. [ABSTRACT FROM AUTHOR]

Purification of seawater and wastewater by solar-driven interfacial evaporation is a promising way to alleviate water scarcity. However, the high cost, complex fabrication methods, and short service life of the materials limit their practical application. Herein, a novel three-dimensional (3D) photothermal aerogel composited of vermiculite nanosheets and polyvinyl alcohol (PVA) precursors have been prepared via freeze-drying and treated by quick pyrolysis for highly efficient solar-driven interfacial evaporation. The vermiculite nanosheets exfoliated from natural clay were used as the skeletal support of the composite aerogels, which are cheap and abundant natural materials. The introduced PVA improves the mechanical properties and produces carbon derivatives after pyrolysis, enhancing the light absorption capacity. The as-prepared aerogels have hierarchical porous structures, impressive mechanical properties, great light absorption capacity, and outstanding salt-rejection ability. The optimized aerogel not only exhibits a high evaporation rate of 2.64 kg m−2 h−1 (normalized to top and side surfaces) under 1.0 sun irradiation with excellent cost-effectiveness at 361.64 g h−1 $−1 but also shows superior performance in treating high-salt (15.0 wt%) brine water and organic dye-contained wastewater. The proposed method provides an attractive and effective way to prepare photothermal aerogels for efficient solar steam generation for mitigating water scarcity issues. • 3D clay-based solar evaporators for desalination were made. • Scalable and low-cost PVPA was prepared via a simple and quick pyrolysis strategy. • The as-prepared PVPA shows excellent evaporation performance and reusability. • The PVPA can treat different concentrations of brine and dye-contained wastewater. [ABSTRACT FROM AUTHOR]

• Aerogels can be easily fabricated via cross-linking vermiculite and MXene. • The pore structures and surface compositions of aerogels can be finely tuned. • Monolithic aerogel has excellent CO 2 storing capacity by boosted hydrate formation. • Degree of water saturation plays the most vital role in hydrate formation. Gas hydrate provides an ideal way for CO 2 capture and storage using water by forming cages via an environment-friendly and energy-efficient hydrate formation process. However, the practical utilization and upscaling of hydrate-based gas storage are impeded by the slow formation kinetics of gas hydrate due to the limited multiphase interface for mass transfer and reaction. Herein, we demonstrated a simple strategy to fabricate composite aerogels assembled of natural vermiculite and MXene nanosheets as the ideal substrate for boosting CO 2 hydrate formation. The structure and surface compositions of vermiculite/MXene composite aerogels were analyzed by XRD, FT-IR, SEM, and XPS. It shows that monolithic pore structures and surface functional groups can be finely tuned by controlling the mass ratio of vermiculite and MXene, leading to an outstanding CO 2 storage capacity of 136.9 v/v (corresponding to 0.121 mol CO 2 /mol water) with enhanced hydrate formation kinetics. The degree of water saturation plays the most vital role in controlling formation kinetics and gas storage capacity. This work provides a reliable method to synthesize aerogels for boosting CO 2 storage via enhanced hydrate formation and sheds light on the structure performance relationship of porous materials for enhancing gas hydrate formation. [ABSTRACT FROM AUTHOR]

• Aerogels can be easily fabricated via cross-linking vermiculite and MXene. • The pore structures and surface compositions of aerogels can be finely tuned. • Monolithic aerogel has excellent CO 2 storing capacity by boosted hydrate formation. • Degree of water saturation plays the most vital role in hydrate formation. Gas hydrate provides an ideal way for CO 2 capture and storage using water by forming cages via an environment-friendly and energy-efficient hydrate formation process. However, the practical utilization and upscaling of hydrate-based gas storage are impeded by the slow formation kinetics of gas hydrate due to the limited multiphase interface for mass transfer and reaction. Herein, we demonstrated a simple strategy to fabricate composite aerogels assembled of natural vermiculite and MXene nanosheets as the ideal substrate for boosting CO 2 hydrate formation. The structure and surface compositions of vermiculite/MXene composite aerogels were analyzed by XRD, FT-IR, SEM, and XPS. It shows that monolithic pore structures and surface functional groups can be finely tuned by controlling the mass ratio of vermiculite and MXene, leading to an outstanding CO 2 storage capacity of 136.9 v/v (corresponding to 0.121 mol CO 2 /mol water) with enhanced hydrate formation kinetics. The degree of water saturation plays the most vital role in controlling formation kinetics and gas storage capacity. This work provides a reliable method to synthesize aerogels for boosting CO 2 storage via enhanced hydrate formation and sheds light on the structure performance relationship of porous materials for enhancing gas hydrate formation. [ABSTRACT FROM AUTHOR]

• Aerogels with tunable surface properties significantly promoted hydrate formation. • C O and –OH were found to dominate nucleation and growth of hydrate. • The finely tuned oxygen-containing groups lead to the enhanced kinetics. • Aerogels exhibit high storage capacity and excellent cycling stability. • Aerogels can be prepared in a large scale for hydrate-based applications. Gas hydrate, composed of water molecule cages, is promising for safe and sustainable gas storage with minor energy consumption. However, the practical utilization of hydrate-based technologies is hindered by the sluggish formation kinetics of gas hydrate. Central to the challenge of utilizing hydrate-based gas storage is developing effective promoters and improving the understanding of the complicated interplay between a promoter's structure and chemical composition. Herein, we reported a simple and scalable strategy to produce pyrolytic composite aerogels assembled from vermiculite nanosheets and sodium alginate as efficient promoters for the methane hydrate formation. Benefiting from the high specific surface area and finely tuned surface functional groups, the as-made aerogels significantly improve methane hydrate formation kinetics with high storage capacity and excellent cycling stability. It is found that the phase change process of water to methane hydrate conversion can be controlled by adjusting the content of carbonyl and hydroxyl groups of the as-made aerogels. Raman spectra were used to elucidate the molecular mechanisms for the enhanced methane hydrate formation due to the interaction between oxygen-containing surface functional groups and water molecules close to used aerogels. This work not only provides an effective way to fabricate aerogel-based promoters for methane hydrate formation but also sheds light on the underlying mechanism of the surface composition dependent performance for improving gas hydrate formation. [ABSTRACT FROM AUTHOR]

The inherently intermittent feature of solar energy requires reliable energy conversion and storage systems for utilizing the most abundant solar energy. Phase change materials are potential solutions to store a large amount of heat produced by solar light. However, few of the phase change materials have the ability to efficiently convert solar energy into heat; additionally, phase change materials need to be encapsulated in porous substrates for enhancing their leaking resistance and photo-to-thermal performance. In this work, monolithic MXene aerogels, fabricated by Al3+ cross-linking and freeze-drying, were used as the encapsulation and photothermal materials. The composites phase change materials of MXene/polyethylene glycol can be made with a large polyethylene glycol loading above 90 wt% with the maximum of 97 wt%, owing to the large porosity of MXene aerogels. The low content of MXene has a limited impact on the phase transition temperature and enthalpy of polyethylene glycol, with an enthalpy retention rate ranging from 89.2 to 96.5% for 90–97 wt% polyethylene glycol loadings. MXene aerogels greatly improve the leaking resistance of polyethylene glycol above its melting point of 60 °C, even at 100 °C. The composites phase change materials also show outstanding cycling stability for 500 cycles of heat storage and release, retaining 97.7% of the heat storage capability. The optimized composite phase change material has a solar energy utilization of 93.5%, being superior to most of the reported results. Our strategy produces promising composite phase change materials for solar energy utilization using the MXene aerogels as the encapsulation and photothermal materials. [ABSTRACT FROM AUTHOR]

• CBCMs significantly improved the hydrate formation kinetics and storage capacity. • Carbonyl groups was identified as the active sites enhancing CH 4 hydrate formation. • Functional groups tuned hydrogen-bonding network results in the enhanced kinetics. The sluggish formation kinetics is a formidable challenge for the practical application of gas hydrate-based technologies for natural gas storage and transportation. Methane hydrates in both nature and labs exclusively form with the assistant of foreign additives via a heterogeneous process. Although the process is common and widely used, it remains unclear what makes a material a good methane hydrate promoter. Additionally, the molecular mechanisms underlying the promoted hydrate formation remain largely unknown. Herein, carbon monoliths (labeled as CBCM) with finely controlled surface functional groups were produced using cellulose as precursors. The oxygen-containing groups have been identified as the active sites enhancing the nucleating ability of methane hydrates. Carbonyl oxygen is pinned down as the most effective functional group in reducing the induction time and enhancing the formation kinetics of methane hydrate. The turned hydrogen bonds between water molecules, which are close to the surface of CBCM, contribute to the enhanced formation kinetics as confirmed by the Raman spectroscopy. The CBCM with optimized carbonyl oxygen significantly improve the methane hydrate formation kinetics and storage capacity with outstanding cycle stability, which are superior than most of the previously reported promoters, particularly in shorter induction time. The finding in this work paves the way for effectively designing promoters and unraveling the underlying mechanism for enhancing gas hydrate formation. [ABSTRACT FROM AUTHOR]

Self-assembly of two-dimensional (2D) nanosheets into three-dimensional (3D) aerogels, can solve the problems of recovery and re-stacking, and fully utilize the potential of high specific surface areas and easily accessible surface sites. However, organic binders have to be added to fabricate aerogels using 2D nanosheets as building blocks, which inevitably limit the performance of 2D nanosheets due to covered surfaces. Herein, we proposed a new strategy to fabricate vermiculite aerogels (VAs) assembled from delaminated vermiculite nanosheets (VNSs) via metal ion induced fast gelation. The cheap and earth-abundant vermiculite was used as the raw materials to produce high-quality nanosheets by high speed shear-mixing. VNSs with a concentration as high as 15 mg/mL were produced. The concentration-dependent gelation performance was studied and showed a critical concentration of 6 mg/mL for gelation and fabricating monolithic aerogels without cracks. It is also found metal ions played critical roles in formation mechanically stable and robust aerogels with trivalent cations, particularly Al3+ being most effective. The edge-surface intertwining VNSs induced by the Al3+ cross-linking endow the VAs good mechanical strength and excellent environmental stability. As fixed adsorbent beds, the VAs show promising performance in fast removing organic dyes from water due to the developed pore structures, large specific surface area, and exposed surface sites. [Display omitted] • Vermiculite aerogels were successfully assembled using a fast and scalable method. • Both nanosheet concentration and the ion type play critical roles in gelation. • Vermiculite aerogels have shown excellent performance in removing organic dyes. [ABSTRACT FROM AUTHOR]

• Fungus and surfactants synergistically promote formation of methane hydrate. • Confined surfactants show improved cyclic stability. • The foaming problem is eliminated by confining surfactants in black fungus. The storage and transportation of natural gas in the form of gas hydrates have the advantages of being safer and more environmentally friendly. However, the slow formation of kinetics has limited the large-scale application of hydrate-based technologies. In this work, we confined water and sodium dodecyl sulfate solutions in black fungus to improve hydrate formation and eliminate the foam problem associated with hydrate decomposition in a surfactant solution. The black fungus effectively increases the gas-liquid contact area, thereby significantly enhancing the hydrate formation kinetics. Raman spectroscopy was used to confirm the promoting role of porous fungus in facilitating CH 4 hydrate formation. The degree of saturation and concentration of confined SDS solution in fungus have critical impacts on turning the induction time of the CH 4 hydration formation and the maximum gas storage capacity. The corresponding mechanisms have been elucidated. Additionally, with porous fungus as the confining substrate, SDS solutions show impressive recycling stability for enhancing hydrate formation. The porous fungus with an excellent promotion performance is highly promising for applications in the storage and transportation of natural gas in the form of hydrates. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical reduction of CO 2 (CO 2 RR) to fuels and chemicals is a promising route to close the anthropogenic carbon cycle for sustainable society. The Cu-based catalysts in producing high-value hydrocarbons feature unique superiorities, yet challenges remain in achieving high selectivity. In this work, Cu@ZIF-8 NWs with highly-exposed Cu nanowires (Cu NWs) and ZIF-8 interface are synthesized via a surfactant-assisted method. Impressively, Cu@ZIF-8 NWs exhibit excellent stability and a high Faradaic efficiency of 57.5% toward hydrocarbons (CH 4 and C 2 H 4) at a potential of −0.7 V versus reversible hydrogen electrode. Computational calculations combining with experiments reveal the formation of Cu and ZIF-8 interface optimizes the adsorption of reaction intermediates, particularly stabilizing the formation of *CHO, thereby enabling efficient preference for hydrocarbons. This work highlights the potential of constructing metals and MOFs heterogeneous interfaces to enhance catalytic properties and offers valuable insights for the design of highly efficient CO 2 RR catalysts. [ABSTRACT FROM AUTHOR]

Ultrathin, transparent, and free‐standing films assembled from low‐dimensional nanomaterials (LDMs) are promising for various applications, including transparent heaters and membranes. However, the intact separation of the assembled films, especially those with controlled ultrathin thickness from deposited substrates, is a tremendous challenge, particularly for fast peeling off via self‐detaching. Herein, we propose a versatile method to rapidly peel off ultrathin assembled LDM films, including three types of carbon nanotubes, vermiculite, Ag nanowires, and carbon nanotube@graphene, by dissolving the MXene interlayer from the layer‐by‐layer filtered MXene/LDM Janus films using diluted H2O2. The MXene sacrificial interlayers play dual roles, including physical isolation of LDM films from filter membranes and the production of bubbles that buoy ultrathin LDM films, making them free‐standing. The integrality and self‐detaching rate of the LDM films are determined by the loading and reactivity of the MXene interlayers. The intact LDM films can self‐detach in 80 s by dissolving the optimized MXene interlayer and producing bubbles. The as‐made free‐standing ultrathin LDM films can be transferred to arbitrary substrates and exhibit outstanding performance as transparent heaters. This scalable method provides an efficient and versatile method to produce ultrathin, transparent, and free‐standing LDM films and finds new applications for the growing MXene family. [ABSTRACT FROM AUTHOR]

• High water recovery can be obtained via cyclopentane hydrate formation. • Halide ions have different capability in hindering hydrate formation. • High purity fresh water can be produced via multi-stage hydrate desalination. Hydrate-based desalination is an attractive and energy-effective method. In order to obtain high water recovery and purity, the desalination and Li+ enrichment performance were examined using single-stage desalination via graphite-promoted cyclopentane (CP) hydrate formation. LiCl, LiBr and LiI aqueous solutions with concentration ranging from 0.01 to 0.6 mol/L were used as brine. The rate for CP hydrate formation is determined by concentration, independent of the type of used salts. Halide ions were found to have the different capability in hindering CP hydrate-based desalination, with an order of Cl− < Br− < I−. The desalination efficiency was improved with increased concentration. Water recovery of 40% can be obtained in 1 h reaction, demonstrating the high efficiency of hydrate-based desalination. The desalination efficiency remains constant at around 70% over 24 h reaction, which can be dramatically enhanced by multi-stage desalination. The graphite powder, as the promoter for hydrate formation shows impressive recycling stability. The finding in this study would be of great help for developing effective desalination processes to produce fresh water and enrich high-value salts via CP hydrates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphene and sodium cholate synergistically accelerate the rapid formation of methane hydrate. • This synergistic acceleration is achieved by increasing partial hydrogen-bonded intermediate water induced by graphene. • Mixed graphene and sodium cholate shows impressive recycling stability for enhancing methane hydrate formation. Gas hydrate is viewed as a promising form to store and transport methane, while the sluggish formation kinetics limits its large-scale utilization. Recently, many nanomaterials have been reported to accelerate the formation of methane hydrate, but their performance is difficult to satisfy the practical application. Additionally, the promoting mechanism of the nanomaterials is yet to be figured out. Here we studied the effect of graphene and sodium cholate on methane hydrate formation. Graphene and sodium cholate show a synergistic effect on methane hydrate formation, corresponding to the induction time halved in the mixture of them than sodium cholate solution. This acceleration was achieved by the increase of intermediate water (IW) induced by the added graphene. IW has the potential to accelerate the nucleation of methane hydrate based on its partial hydrogen-bonded structure. Meanwhile, the mixture of graphene and sodium cholate express excellent recycling stability during the repeated methane hydrate formation − dissociation. The insight of this study can apply to develop high-efficiency kinetic additives for methane hydrate. [ABSTRACT FROM AUTHOR]

Interfacial water evaporation, powered by solar energy, holds great promise to extract freshwater from seawater on a global scale. It has the potential to address the world's water scarcity challenges using renewable energy. While the ideal design of evaporator materials is critical to the interfacial vaporization desalination, tailoring the structures and compositions of solar evaporators and figuring out the structure/composition-performance relationship of evaporators remains unexplored. Herein, 3D macroporous "brick-concrete" MXene/sodium alginate aerogel (MSA) evaporators were designed and fabricated with constant MXene content and varying polymer loading. The as-made MSAs show sodium alginate-dependent evaporating performance with an optimum evaporation rate of 3.28 kg m−2 h−1 (1 sun). This exceptional rate is attributed to several factors, including enhanced light absorption, optimized pore sizes, reduced enthalpy of evaporation and improved water transport. The water molecule states and hydrogen bonding network in the aerogels can be tuned by their compositions, resulting in the reduced evaporation enthalpy, the monolithic structures with controlled thermal conductivity facilitate the exploitation of environmental energy, leading to the high evaporation rate. Our study not only establishes design principles for achieving superior evaporation performance, but also sheds light on the relationship between structures, compositions, and performance of solar evaporators. • The "brick-concrete" structures were used to optimize the pore sizes of the 3D photothermal evaporators. • The functions of MSAs in water transport and hydrogen bond activization were systematically analyzed. • The as-prepared MSAs show excellent evaporation performance and reusability. [ABSTRACT FROM AUTHOR]

The local reconfiguration of charge density achieved by Cu-O-Zn heterointerface derived from metal-organic frameworks, balances the CO 2 RR and HER processes, enabling efficient conversion from CO 2 to syngas with controllable CO/H 2 ratios. [Display omitted] • Cu-ZnO catalyst was successfully prepared by MOF-derived strategy. • MOF-derived porous carbon restricts the nanoscale size of bimetallic particles. • The porous carbon skeleton ensures the exposure of Cu-O-Zn interface sites. • Cu-O-Zn interface modulates the adsorption of the key intermediates. • The Cu-ZnO catalyst realize high CO selectivity and wide CO/H 2 ratios. Electrochemical reduction of CO 2 (CO 2 RR) to syngas is a promising approach for mitigating excessive CO 2 emissions and producing liquid fuels and industrial chemicals. However, achieving a suitable CO/H 2 ratio in a one-step reaction and a high current density remains a significant challenge. Herein, we prepare Cu-ZnO catalyst with Cu-O-Zn heterogeneous interface derived from metal-organic frameworks (MOFs) to catalyze the conversion of CO 2 to syngas. By constructing a Cu-O-Zn heterointerface, the bimetallic electronic configurations are modulated, wherein the reconfiguration of electron density induced by electron delocalization enhances the stabilization of *COOH intermediate and the production of CO. Moreover, the porous carbon derived from MOFs restricts the nanoscale size of bimetallic particles, ensuring abundant Cu-O-Zn heterointerface and exposed active sites, while preventing nanoparticle detachment and aggregation during the reaction process. The obtained catalysts realize high CO selectivity (75.6% of CO Faradaic efficiency) and wide CO/H 2 ratio (0.38–3.22) within a relatively narrow potential window and demonstrating excellent stability. This study offers insights into the rational design of high-performance multiphase electrocatalysts. [ABSTRACT FROM AUTHOR]

Gas hydrate-based CO 2 storage, using only water cages, provides an environmentally friendly and energy-efficient solution to reduce greenhouse gas emissions. However, the sluggish formation kinetics of gas hydrate is hindered by the limited reaction interfaces, thereby impeding the practical utilization of hydrate-based greenhouse gas storage. Herein, we reported a novel strategy to fabricate natural vermiculite and tannic acid composite aerogels as the effective substrates for boosting CO 2 hydrate formation. The results show that the formation kinetics of CO 2 hydrate in the aerogels exhibits composition dependence and an outstanding CO 2 storage capacity of 130.1 v/v (corresponding to 0.114 mol CO 2 /mol water). Inverse gas chromatography was used to analyze the surface energy and its components of the aerogels. Raman spectra and nuclear magnetic resonance were used to unravel the water molecule assembly and states. The CO 2 uptake capacity can be further improved by compressing the aerogel to 75 % of the original volume, showing an impressive storage capacity of 146.8 v/v. The as-made aerogels demonstrated outstanding cycle stability and short induction time for CO 2 hydrate formation. The results of this study pave the way for designing effective CO 2 hydrate promoters and facilitating promising CO 2 capture and storage technologies via gas hydrate. [Display omitted] • Monolithic aerogel can be easily fabricated by cross-linking vermiculite nanosheets. • The surface compositions and pore structures of aerogels can be finely tuned. • Aerogels have excellent CO 2 storing capacity by boosting hydrate formation. • Hydrogen bond arrangement plays the most vital role in hydrate formation. [ABSTRACT FROM AUTHOR]

Natural gas hydrates are a potential future energy modality with the advantages of clean burning and large resource reserves and have attracted worldwide attention. Natural gas hydrates formation and dissociation impact the skeletal structure and mechanical properties of porous media sediments. In addition, there is a synergistic effect between the migration of fine clay particles in porous media and hydrate behavior. In this study, methane hydrate was examined in-situ using a low-field nuclear magnetic resonance system in the presence of two suspensions of clay particles with different stability. The results showed that clay particles impacted methane hydrate formation and dissociation and the pore structure of porous media. Hydrate nucleated preferentially in large pores, causing them to split into smaller pores; the presence of clay particles, especially illite, improved the water conversion rate. The results indicated that water content in large pores increased after hydrate dissociation but was discontinuous among different pores. When illite was present, the distribution was more continuous; when montmorillonite was present, the water distribution of the large pores was similar to that of the original state. This work increases our understanding of the kinetics, water migration, and pore structure alteration of methane hydrate formation and dissociation in sediments with clay particles and provides support for the safe and efficient development of natural gas hydrates. • Clay particles impacted methane hydrate formation and dissociation • Hydrate nucleated preferentially in large pores • Clay particles, especially illite, improved the water conversion rate • Water content in large pores increased after hydrate dissociation but was discontinuous among different pores [ABSTRACT FROM AUTHOR]

Hydrate-based CO2 capture from large emission sources is considered a promising process for greenhouse gas mitigation. The addition of nanoparticles may promote or inhibit the formation of hydrates. In this work, CO2 hydrate formation experiments were performed in a dual-cell high-pressure reactor. Non-modified, hydrophilic modified and hydrophobic modified aluminum oxide (Al2O3) nanoparticles at different concentrations were added to assess their promoting or inhibitory effects on CO2 hydrate formation. The equilibrium temperature and pressure, induction time, and total gas consumption during CO2 hydrate formation were measured. The results show that the presence of Al2O3 nanoparticles exerts little effect on the phase equilibrium of CO2 hydrates. Under the experimental conditions, the addition of all Al2O3 nanoparticles imposes an inhibitory effect on the final gas consumption except for the 0.01 wt% addition of hydrophilic modified Al2O3 nanoparticles. The induction time required for the nucleation of CO2 hydrates mainly ranges from 70 to 90 min in the presence of Al2O3 nanoparticles. Compared to the absence of nanoparticles, the addition of non-modified and hydrophilic modified Al2O3 nanoparticle reduces the induction time. However, the hydrophobic modified Al2O3 nanoparticles extend the induction time. [ABSTRACT FROM AUTHOR]

Abstract Desalination via hydrate processes is promising in producing freshwater at low energy cost. However, it is a great challenge to instantaneously produce and form large amount of hydrates in short time, particularly with salts presence. In this study, we used cheap and easily separated graphite particles to promote hydrate based desalination. The added graphite can promote the formation of hydrate, greatly shortening the induction time. The desalination efficiency was also enhanced due to the introduced graphite. Combined graphite and stirring, both the desalination efficiency and water conversion ratio were boosted. The impact of particle sizes of graphite on hydrate formation was found to be different at static state and stirring. The proposed hydrate based desalination is almost independent on treated volume. Additionally, this method can use the nature chilling, which is potential in further reducing the energy cost of desalination via hydrate. The findings in this study would help rationally choose and design promoting agents and hydrate processes for facilitating hydrate formation and desalination via hydrates. Highlights • Introduction of graphite boosted the hydrate formation rate. • Graphite increased desalination efficiency and water conversion ratio. • The particle size of graphite played critical roles in enhancing desalination via hydrate process. [ABSTRACT FROM AUTHOR]