Owing to the heterogeneity of methane hydrate reservoirs in the South China Sea, hydrate and silty clay particles mostly exist in the form of interbedded reservoirs. Permeability is a decisive factor for the efficiency of interbedded methane hydrate deposits. Therefore, using montmorillonite as the simulated sediment material, permeability measurements of interbedded sediments with different methane hydrate distributions and effective stresses were carried out for the first time in this study. By comparing with homogeneous sediments, the permeability evolution of interbedded sediments under different hydrate distributions and effective stresses is explored, and the effect of methane hydrate dissociation on the permeability of interbedded sediments is analyzed. The results show that the permeability of interbedded sediments with different hydrate saturation levels has little difference and is almost the same as that of pure soil sediments. With the increase of effective stress, the porosity of methane hydrate interbedded sediments decreases and permeability damage is caused, but the final permeability damage is less obvious than that of homogeneous hydrate sediments. In addition, the gas slip effect exists in methane hydrate interbedded sediments. Moreover, the dissociation of methane hydrate causes clay swelling, which leads to the decrease of interbedded permeability, but the degree of permeability damage is lower than that of homogeneous sediments. The results of this study provide a theoretical basis for the development and utilization of interbedded methane hydrate sediments in the South China Sea.

Hydrogen sulfide (H2S) is a hazardous and corrosive byproduct generated during heavy oil recovery, particularly during hot water flooding. Previous studies on factors influencing H2S generation during hot water flooding have been mainly focused on high temperatures (>250 °C), which may not accurately represent reservoir conditions. Moreover, the concentration of H2S produced by hot water flooding at low temperatures exceeds the standard. In this study, experiments were conducted on hot water flooding at low temperatures (110–150 °C). The mechanism of reactants and reaction conditions on H2S generation was investigated. The results showed that thermochemical sulfate reduction (TSR) was the primary reaction type responsible for H2S generation, while aquathermolysis and pyrite oxidation reactions weakly or did not occur. The reactivity of TSR was directly proportional to reaction temperature and time, while inversely proportional to reaction pH. The formation of oxidants ([MgSO4]CIP and HSO4–) was also found to be crucial for TSR initiation. Unstable organic sulfur-containing compounds were oxidized to produce CO2, H2S, SO3, and solid bitumen, which further sustained the autocatalytic reaction. Low temperature TSR was found to consume the saturated fraction in heavy oil and convert inorganic sulfur to organic sulfide. The increase in pH inhibited the conversion of inorganic sulfur to organic sulfur, resulting in a higher percentage of the saturated fraction. This study provides new insights into the low temperature TSR reaction mechanism and the origin of H2S, which can aid in better understanding and mitigation of the associated risks during heavy oil recovery.

Although the coal pore structure is attracting the attention of researchers, studies on the multifractal and gas adsorption/desorption capacity are relatively few. In this study, multifractal characteristics were analyzed, and their effects on gas adsorption/desorption were discussed. The results showed that metamorphism and tectonism affected gas adsorption/desorption by changing the coal pore structure. The limit gas adsorption volume and initial desorption rate of tectonic coals increased by 3.9%–23.9% and 1.96–2.7 times, respectively. The information dimension (D1), correlation dimension (D2), and classical Hurst index gradually decreased with metamorphism and tectonism, while the Hausdorff dimension and Δα gradually increased, indicating that pore size distribution (PSD) was more decentralized or inhomogeneous. The evaluation results of the correlation between multifractal parameters and complexity confirmed its accuracy in assessing pore complexity. Multifractal parameters have a significant impact on gas adsorption/desorption capacity overall, mainly by reflecting the concentration degree, local density, and homogeneity of pores.

Silicon oxide (SiOx) is a widely researched Si-based anode due to its simplicity in synthesis, cost-effectiveness, and high theoretical capacity (2680 mAh g–1). However, its poor electrical conductivity and up to 200% volume expansion are significant obstacles to its practical application. Herein, a porous carbon-rich SiOx/C anode was derived from the sole source of para grass using one-step calcination. Para grass offers a sustainable option for biomass, with its considerable lignocellulose and silica compounds that can be used as a renewable precursor. The synthesized SiOx/C shows a high carbon content of ∼89.51 wt % and a mesoporous structure with a surface area of ∼1235 m2 g–1. The high carbon content provides a conductive network, while the porous structure enhances mechanical durability during cycling and provides more sites for lithium-ion insertion/extraction. In a half-cell configuration, the SiOx/C demonstrates a specific capacity of 716 and 299 mAh g–1 at 200 and 1000 mA g–1, respectively. Full-cell configuration of Li-ion batteries with a para grass-derived SiOx/C anode and LFP cathode exhibited a capacity of 129 mAh g–1 at 0.1C and retained 80% of its capacity after 150 cycles at 1C. This study highlights the synthesis of anode materials from sustainable and cost-effective resources with favorable performance and stability.

VS4, also known as patronite, is a widely studied nanostructured material due to its fascinating high theoretical capacity. VS4 has been getting much attention in supercapacitor as well as battery applications due to its parallel one-dimensional chain-like structure with an interchain spacing of 5.83 Å, which helps to provide space for accommodating the insertion/extraction of ions. There have been a number of scientific reports published on VS4 and VS4-based nanocomposites for energy storage applications recently. In this aspect, here we summarize the charge storage properties of VS4 and its nanocomposites including rGO, CNTs, MXenes, metal chalcogenides, and other carbon-based composites for supercapacitor applications. Moreover, challenges and future perspectives of VS4-based electrode materials are included in the conclusion.

The study of fractal percolation in shale pores is beneficial to the exploration and development of shale oil and gas, and the application of the fractal dimension to the characterization of percolation capacity can help to clarify the mechanism of gas percolation in shale. In this study, gas adsorption (CO2 and N2) and high-pressure mercury injection porosimetry (MICP) and gray correlation method are mainly used to investigate the shales of the Lower Silurian Longmaxi Formation in the Luzhou–Changning area in the southern Sichuan basin. In this study, we establish a new template to evaluate the degree of matching between the template and actual geological data considering the effects of shale fractal dimension, tortuosity, the Knudsen number (Kn), and porosity on permeability. The results reveal three observations. First, the deep organic shale pores of the Longmaxi Formation in the area have obvious multiscale fractal characteristics, and the fractal dimension (D) values reflect the complexity of shale pores at different scales. There are significant differences in the fractal dimensions among the three shale lithofacies types. Siliceous shale of D1 with the highest micropore fractal dimension, D2 with mesoporous, and D3 with macroporous indicate more complex pore structures, which provide plenty of gas adsorption and enrichment spaces. These structures are conducive to gas accumulation. Second, there are complex correlations between the total organics content (TOC), the mineral composition, and the inhomogeneity parameters of shale. The TOC, siliceous mineral content, and inhomogeneity parameters of porosity, tortuosity, Kn, and D are positively correlated. The carbonate mineral content and clay mineral content are negatively correlated with the inhomogeneity parameters porosity, tortuosity, Kn, and D. Third and finally, based on correlation analysis, the three main parameters of D, porosity, and tortuosity were ultimately determined, and corresponding templates were established. It reflects that permeability, which is a parameter of seepage capacity, has a high correlation with fractal dimension, tortuosity, and porosity.

In the electrochemical energy storage system, redox-active organic polymers have great attraction due to their eco-friendly, easily available raw materials, variation of design architecture with tailoring their molecular structure, and excellent redox-active functional groups. In this paper, we designed a novel pyridine-functionalized naphthalene diimide cross-linked polymer as an electrode material. The synthesized naphthalene diimide appended the pyridine cross-linked polymer with three-dimensional network structures, showing an outstanding electrochemical performance in SC applications. The monomer NDI-PY-AC is synthesized by using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NDA) and PY-AC by a simple imidization–condensation reaction. Furthermore, the PNDI-PY-AC polymer was synthesized via radical polymerization using AIBN as an initiator. The cross-linked PNDI-PY-AC polymer was confirmed using solid-state 13C NMR and Fourier transform infrared (FT-IR) spectroscopic techniques. The PNDI-PY-AC polymer morphology of the material was examined by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images. The specific surface area and porosity of the polymer were confirmed by the Brunauer–Emmett–Teller (BET) method. The cross-linked-type morphology of the polymer resolved the solubility issue of the electrode material in the electrolyte. The practical applicability of PNDI-PY-AC is evaluated using symmetric two-electrode Swagelok cell assembly. The PNDI-PY-AC/GF electrode acts as a cathode and anode in the solid-state synchronous condenser (SSC) device, which shows a specific capacitance (Csp) of 202.85 F g–1 at 0.5 A g–1 current density. The SSC device shows a high energy density of 49.69 Wh kg–1 with a power density of 1259.99 W kg–1 at a discharge current density of 0.5 A g–1. We observed that the PNDI-PY-AC/GF electrode exhibited an original capacitance retention of 92.86% after 5000 GCD cycles at 2 A g–1 current density.

Because of their high energy densities and specific capacities, lithium–sulfur (Li–S) batteries have recently received an extensive amount of research. The best way to boost battery performance is by altering the electrode materials. The adoption of 2D material-based heterostructures has attracted significant attention for increasing electrochemical performance and preventing the shuttle effect. Therefore, a summary of the link between the specific properties of 2D material heterostructures and electrochemical performance is required for the development of next-generation Li–S batteries. The present research focuses on the latest developments that boost the performance of Li–S batteries by using the unique features of 2D material heterostructures. This evaluation also categorizes several meticulously selected 2D materials with specific properties. Some solutions have been developed to overcome the difficulties of insulating intermediates, polysulfide shuttle, and sluggish kinetics. Superior conductivity, tunable functional groups, and exceptional flexibility are some of the most crucial elements in boosting electrochemical performance.

Inorganic salt hydrates are promising phase-change materials (PCMs) for thermal energy storage due to their high latent heat of fusion. However, their practical application is often limited by their unstable form, dehydration, large supercooling, and low thermal conductivity. Porous melamine foam and its carbonized derivatives are potential supporting porous materials to encapsulate inorganic salt hydrate PCMs to address these problems. This work investigates the effect of pyrolysis temperature on the morphology and structure of the carbonized foams and their thermal energy storage performance. Pyrolysis of melamine foam at 700–900 °C leads to the formation of crystalline sodium cyanate and sodium carbonate particles on the foam skeleton surface, which allows the spontaneous impregnation of the carbon foam with molten CaCl2·6H2O. The form-stable foam-CaCl2·6H2O composite effectively suppresses supercooling and dehydration, demonstrating the efficacy of carbon foam as a promising supporting material for inorganic salt hydrate PCMs.

Surfactants are commonly used for enhanced oil recovery (EOR) applications in carbonate hydrocarbon reservoirs due to their ability to reduce oil/water interfacial tension (IFT) and/or alter rock wettability toward more water-wet conditions. They are usually used as formulations consisting of more than two surfactants to achieve optimum performance. Although this approach may result in extra recovery in coreflooding experiments, there is a risk of chromatographic separation and potential phase separation when these surfactants are injected into the reservoir. The current study, however, focuses on injecting a single component ethoxylated quaternary ammonium cationic Gemini surfactant (GS) or a betaine-type zwitterionic surfactant (ZIS), both synthesized in-house, to mitigate these potential issues. Several coreflooding experiments were conducted using Indiana limestone samples at 100 °C, pressures greater than 3000 psi, and seawater and formation water salinities of 57,745 ppm and 213,768, respectively. Continuous injection of either surfactant solution (at 2500 ppm in seawater) after seawater flooding recovered almost 11–12% of the initial oil in the core (OOIP). The results demonstrate that the GS or the ZIS alone can achieve this relatively high oil recovery without the need for additional cosolvent(s) or cosurfactant(s), unlike most of the previously developed surfactant formulations. Injecting a one-pore-volume slug of a standard acrylamide copolymer at 2000 ppm between the seawater and the surfactant floods increased the oil recovery by either surfactant to around 16–17% OOIP. This improvement in oil recovery was mainly due to wettability alteration from oil-wet to intermediate-wet conditions, as revealed by the contact angle and oil/water IFT measurements. Effluent analysis of the produced aqueous phase showed surfactant dynamic retention values of 0.44 and 0.61 mg/g-rock of both the GS and the ZIS, respectively. Such high oil recovery and low dynamic retention reflect the high efficiency of the GS and the ZIS for EOR applications in carbonate reservoirs.

Hydrate-based separation and capture technology, as a green and economical gas separation technology, can be used to purify biogas by removing CO2 to increase the calorific value and energy density. To achieve pilot-scale biogas separation, a 15 L pilot-scale reactor with novel jet impingement stream was designed for fast and efficient CH4 recovery and CO2 capture and pure CH4 was obtained by multistage separation in this work. Hydrate nucleation and growth were enhanced by jet impingement stream in aqueous solution with 5.0 wt % tetrabutylammonium bromide. The space velocity of the reactor reached a maximum value of 557 h–1; the gas uptake reached up to 1.00 mol/L at 4.0 MPa; and the fastest time to reach 80% of the rate of gas uptake was about 2.5 min at 3.0 MPa and 277 K. The effects of the pressure and temperature driving force on the CH4 concentration in residual gas, CH4 recovery rate, CO2 capture ratio, and gas hydration rate were studied. By a four-stage hydrate-based gas separation process, the CH4 concentration could be increased from 50.0 to about 95.1%. This work provides insights for the industrial application of continuous hydrate-based biogas separation.

Due to the current worldwide environmental problems caused by high emissions of polluting gases such as CO, NOx, and SOx, resulting from the combustion of fossil fuels, many organizations and governments have established standards aimed at producing cleaner and more environmentally friendly fuels. These standards focus on eliminating hazardous substances, particularly the sulfur compounds in diesel, as they are among the most harmful organic compounds to both human health and the environment. Hydrotreating is the main refinery process used to produce ultralow sulfur diesel. For proper modeling and simulation of this process, it is mandatory to develop adequate kinetic models that include all the reactions taking place during the hydrotreating of gas oil, as well as the removal of the most refractory compounds present in the chemical composition of diesel, such as 4-MDBT and 4,6-DMDBT. This work reports an exhaustive discussion of the kinetic models of hydrotreating reactions for the production of ultralow sulfur diesel reported so far in the literature. The main topics include the reaction systems, type of catalysts, and operating conditions. A comparison of the reported kinetic parameters was also carried out. Finally, a set of kinetic models to be considered for the simulation of the hydrotreating process to produce ultralow sulfur diesel is proposed.

Nowadays, most of the hydrogen is obtained from fossil fuels. At the same time, the effort and resources dedicated to the development of sustainable hydrogen manufacturing processes are rapidly increasing to promote the energy transition toward renewable sources. In this direction, a potential source of hydrogen could be hydrogen sulfide, produced as a byproduct in several processes, and in particular in the oil extraction and refinery operations. Methane reforming using H2S has recently attracted much interest for its economic and environmental implications. Its conversion, in fact, provides a viable way for the elimination of a hazardous molecule, producing a high-added value product like hydrogen. At the same time, some of the still open key aspects of this process are the coke deposition due to thermal pyrolysis of methane and the process endothermicity. In this work, the methane reforming with H2S by co-feeding sulfur is investigated through a detailed thermodynamic analysis as a way to alleviate the critical aspects highlighted for the process. A parametric analysis was conducted to assess the best thermodynamic conditions in terms of pressure, temperature, and feed composition. Changing the sulfur, H2S, and methane feed composition can enhance the system by improving the hydrogen production yield, reducing the carbon and sulfur deposition, increasing the H2S removal efficiency, and reducing the necessary thermal duty.

The increasing demand for renewable energy technologies to safeguard the natural world has led to electrocatalysis’s emergence as a promising hydrogen generation method. Recently, metal–organic frameworks (MOFs) have attracted interest as electrocatalysts due to their unique characteristics, including expansive surface areas, exceptional porosity, and readily modifiable optical and electronic properties. This review comprehensively summarizes MOFs’ recent improvement in heterogeneous catalysis and their composites/derivatives for promoting the high efficiency of the hydrogen evolution reaction (HER). Furthermore, a profound assessment of the challenges and expectations for the development of MOF-based electrocatalysts is provided.

A three-dimensional electrolytic cell model coupling the two-phase mass transportation behaviors in the unitized regenerative fuel cell is established. This simulation work mainly studies the distribution rule of species inside the electrolytic cell and analyzes the liquid water saturation in inlet and working voltage, respectively. The results show that the high saturation of liquid water at the inlet can increase the oxygen concentration in the catalytic layer on the oxygen side, and the oxygen concentration gradually reduces following the direction of the catalytic layer to the gas channel, and the oxygen concentration is increased with the direction from the inlet to outlet. When the cell voltage increases from 1.35 to 1.95 V, from the catalytic layer to the gas channel, the change rate of liquid water saturation increases from 0.38 to 12.89%, the change rate of hydrogen concentration increases from 0.37 to 1.70%, and the change rate of oxygen concentration decreases from 90.48 to 80.48%. It is concluded that with the increase of electrolytic cell voltage, the gas production rate increases. On the hydrogen electrode side, the high gas yield makes it easier for hydrogen discharge from the cell.

Acidic nitrogen electrofixation offers the benefits of abundant proton sources and improved solubility of N2 that can facilitate the reaction kinetics at three-phase interfaces. However, excessive protons would simultaneously boost competitive hydrogen evolution that consume electrons otherwise for nitrogen electrofixation, leading to low selectivity to ammonia. In this paper, we report an acid-stable ebonex (Ti4O7) characteristic of excellent catalytic performances in a 0.1 M HCl electrolyte (pH 1). With the incorporation into continuous-flow cells, the catalyst demonstrates an optimal faradaic efficiency of 23.57% and a large ammonia yield rate of 45.52 μg h–1 cm–2, which is 2 orders of magnitude higher than that in traditional H-type cells. A further mechanism study has been conducted using density functional theory (DFT) calculations and X-ray absorption near-edge structure (XANES), which indicate the structural advantages of ebonex,such as intrinsic electrical conductivity and low oxidation valence of Ti and Jahn–Teller-type structural distortion. Consequently, the ebonex catalyst can suppress hydrogen evolution, leading to a favorable associative alternating nitrogen electrofixation pathway with the rate-limiting step of N2* → NNH*.

Currently, precious metal catalysts Pt/C and RuO2/IrO2 are considered efficient catalysts for oxygen reduction reaction (ORR). However, their high cost, scarcity, and poor stability hinder their wide application. Therefore, a simple method to prepare bimetallic oxide nanoparticles as electrodes instead of precious metals is of significant importance for electrocatalysis at present. Here, we use graphene nanosheets as carbon precursors, which can exhibit excellent ORR performance by taking advantage of the empty orbitals of the samarium f-layer, which will result in a high specific surface area due to the use of templates. Therefore, in the preparation process, samarium oxide- and iron oxide-encapsulated nanosheets are formed from samarium and iron coordination polymers, respectively. Moreover, the specific Brunauer–Emmett–Teller effective active sites and the synergistic interaction between samarium oxide and iron oxide also promote ORR kinetics This novel rare earth transition-metal nanoparticle-encapsulated ORR catalyst with a conductive carbon matrix (SmFeOx@CN-5) is attractive for zinc–air battery applications.

The spontaneous imbibition process involves the fluid flow driven by gravity and capillary forces between the matrix and fractures, which is a critical mechanism in oil production in naturally fractured reservoirs (NFRs). Previous studies have explored how various rock and fluid parameters, such as temperature, permeability, connate water saturation, and initial wettability, impact the performance of low salinity water in NFRs using spontaneous imbibition tests. In this particular study, we aimed to investigate the influence of pH on wettability alteration and oil recovery in carbonate-fractured porous media through imbibition at high temperatures. To accomplish this, we utilized a combination of imbibition tests, ion chromatography analysis, contact angle study, and ξ-potential and pH value measurements to verify changes in fluid–rock interactions and evaluate the driving mechanisms of incremental oil recovery by low salinity water at different pH conditions. Our test results have demonstrated that the ultimate recovery factor for each brine remains consistent regardless of the pH levels of the brine solution. However, we observed a significant variation in the oil recovery rate by imbibition. This suggests that the pH of the contacted brine has an impact on the dominant recovery mechanism. Our analysis of ion chromatography and data on the contact angle, ξ-potential, and pH variation has indicated that calcite dissolution and the alkali effect are the primary mechanisms at different pH values. At high pH conditions, the production rates are initially low due to the alkali effect, but they increase as calcite dissolution becomes active. In contrast, under low pH conditions, the recovery rate decreases during production due to the activation of the alkali effect.

Ship exhaust gas greatly threatens human health and the environment. The ozone/urea system has the advantages of strong oxidability, excellent reducibility, and low reductant consumption. This paper thoroughly studied the effects of urea concentration, O3 concentration, initial pH, temperature, O2 concentration, SO2 concentration, and initial NO concentration on NOx removal efficiency using the ozone/urea system. Moreover, this paper conducted a systematic study on the conversion proportion of NOx into nitrate and nitrite, which is very important for the ship NOx wet method. Urea concentration and O3 concentration played important roles in NOx removal efficiency. Weak acid and weak alkali media could effectively improve NOx removal efficiency, but the reasons were completely different. As the temperature increased, the NOx removal efficiency initially decreased and subsequently increased. Besides, the increase of temperature and initial pH could decrease the conversion proportions of NOx into nitrate and nitrite. The increase of SO2 concentration could not only reduce the NOx removal efficiency but also increase the conversion proportion of NOx into nitrate. However, increasing SO2 could significantly decrease the conversion proportion of NOx into nitrite. Under the optimal conditions of this paper, the NOx removal efficiency reached 97.8% and the conversion proportion of NOx into nitrate was only 20.39%. In addition, the urea content was just 0.3 mol/L, which was far lower than that in the prior study. This illustrated that the ozone/urea system had excellent application potential in marine exhaust gas purification.

Membrane technology for carbon capture has been favored to mitigate climate change attributed to the greenhouse effect in recent years. The implementation of composite membranes with a selective layer made from CO2-selective polymers and nanofillers is gaining particular interest for efficient CO2 capture, with the benefits of easy processability, cost-effectiveness, and excellent separation performance. Graphene oxide (GO) with abundant oxygen-containing functional groups exhibits tremendous potential for enhancing mechanical and transport properties when incorporated into the polymeric matrix. Herein, a GO-reinforced polyacrylamide/poly(vinyl alcohol)/polysulfone (PAM/PVA/PSf) composite membrane was developed with a focus on improving the CO2/N2 separation performance. The membrane performance was tested with mixed gas (10/90 vol % CO2/N2) under humidified conditions. The effects of the preparation parameters (e.g., GO content and pH of the casting solution) and the operating parameters (e.g., feed flow rate, feed pressure, temperature, and relative humidity) were systematically investigated and further optimized to identify the optimal condition for post-combustion carbon capture. The best membrane performance with a CO2/N2 selectivity of 65 and a CO2 permeance of 55 gas permeance units (GPU) at 2 bar and 30 °C was documented in this study. The development of CO2-selective composite membranes may address the challenges associated with the upscaling of membrane technology for potential industrial carbon capture.