Abstract CH4/NH3 cofiring represents an effective technical approach to overcome the inferior combustion characteristics of NH3. The combustion characteristics and pollutant formation mechanism during the cofiring constitute important research directions. Hence, it is of considerable significance to gain a comprehensive understanding of the CH4/NH3 cofiring and its mutual influence mechanism. This paper first demonstrates that the general “atmospheric type” blending model in the existing literature may lead to extreme hypoxia during the simulation, thereby overestimating the pollutant formation characteristics. Compared with the “fuel-type” blending model proposed in this paper, it is believed that the new model can precisely analyze the cofiring and reaction mechanism of multiple fuels. Subsequently, the “fuel-type” blending model was used to systematically study the effects of temperature, ammonia blending ratio (ENH3), and equivalence ratio (φ) on the cocombustion. Third, by sorting out the reaction network, it was discovered that under the stoichiometric condition, CH4 and NH3 react independently of each other, which is distinct from the phenomenon in the “atmospheric type” blending model. Contrarily, in the fuel-rich scenario, a coupling mechanism occurred between CH4 and NH3. NO can react with the excess CHi groups in the system through NO + CHi → CHiNO → CHiN → HCN/CN, then decouple to generate CO and N/NH, and then further reduce to N2. Finally, the C–N coupling mechanism was investigated to correct the Okafor mechanism and improve the prediction effect of NO and HCN. These findings not only provide a reference for the subsequent ReaxFF MD study of multiple fuels to construct reaction systems in reality but also provide solutions for reducing NO emissions from CH4/NH3 in actual industry.
Abstract A comparative evaluation of depositional controls and pore evolution in marine shales is essential for understanding differential shale-gas enrichment in South China. This study investigates the Lower Silurian Longmaxi Formation and the Lower Cambrian Niutitang Formation in northwestern Guizhou to clarify the controls on depositional environment, organic matter (OM) enrichment, and reservoir quality. Integrated analyses, including X-ray fluorescence elemental geochemistry, field-emission scanning electron microscopy, low-temperature nitrogen adsorption, and thermal maturity assessment, were conducted on 210 samples from wells XY1 and RY2. Results show that the Niutitang Formation was deposited under more strongly restricted and reducing conditions with higher paleoproductivity and higher total organic carbon (TOC) contents (1.28–11.8 wt %, average 5.58 wt %), but it also exhibits significantly higher thermal maturity, with equivalent vitrinite reflectance (EqRo) values of 2.13%–3.41% (average 2.92%). In contrast, the Longmaxi Formation formed in a semi-restricted reducing setting with moderate paleoproductivity, lower TOC, and relatively lower maturity (EqRo 2.01%–2.65%, average 2.24%). Despite lower TOC abundance, the Longmaxi Formation displays superior reservoir properties: higher Brunauer–Emmett–Teller (BET) specific surface area (average 16.95 m2/g), and much larger average pore diameter (50.77 nm versus 4.80 nm), together with well-developed honeycomb-like organic pores and microfractures. Conversely, the Niutitang Formation is characterized by excessive thermal evolution, severe deterioration of organic pores, and pore space dominated by inorganic intraparticle pores. These results indicate that thermal maturity exerts a stronger control than OM abundance on reservoir quality in overmature marine shales. Accordingly, the Longmaxi shale is more favorable for free-gas enrichment, whereas Niutitang shale exploration should target relatively low-maturity and shallowly buried areas around paleo-uplifts. This framework provides practical guidance for sweet-spot prediction in overmature marine shale-gas systems within structurally complex regions.
Abstract Shallow methane leakage is a topic of great concern for governments and the public worldwide. Upward methane leakage can induce hydrate formation, enabling high-density carbon sequestration but also causing significant changes in fluid saturation and reservoir properties. However, existing studies lack key conclusions about the dynamic prediction of saturation during upward methane migration. Therefore, the formation characteristics and saturation prediction of methane hydrates in muddy cores at different flow rates were studied. The results show that lower gas flow rates are more conducive to hydrate formation, which is attributed to sufficient gas–liquid contact and enhanced mass transfer. The maximum increase in hydrate saturation is 47.43%, and the maximum decrease in permeability (increase in damage coefficient) is 65.99% (27.48%). Methane hydrate formation leads to a decrease in permeability and induces an increase in the inlet pressure nonpressurization gradient, with a maximum pressure difference of 5.85 MPa. At the same time, the permeability and hydrate saturation comply with K = K0((1 – Sh)/(1 + 2Sh))2.5, and the measured values are all within the 95% prediction band. On the basis of the coupled relationship between hydrate saturation and inlet pressure during the flow process, a new hydrate saturation prediction method is proposed (R2 > 0.98). Orthogonal experiment results show that the gas flow rate has the greatest influence on the hydrate saturation, while the outlet pressure has the least influence. This study provides a constructive solution for predicting the hydrate saturation during the upward leakage process of methane.
Abstract The continuous rise in atmospheric carbon dioxide (CO2) concentrations has emerged as a worldwide environmental concern, underscoring the urgent need for innovative capture technologies. Activated carbons derived from renewable biomass feedstocks offer a sustainable and low-cost route for developing efficient CO2 adsorbents. In this work, we report the synthesis of microporous activated carbons from waste sugarcane bagasse via ZnCl2-assisted activation, exploring three pathways: direct activation, precarbonization prior to activation, and hydrothermal carbonization followed by activation. Compared with conventional KOH activation, ZnCl2 enabled the development of well-defined microporosity at 600 °C, a substantially lower temperature than that typically required for KOH (800–900 °C). Systematic optimization of the synthesis conditions enabled precise tuning of the pore structure. The optimal sample obtained via hydrothermal carbonization–activation route exhibited a high specific surface area of 2714 m2/g, with micropores contributing about 85% of the total porosity. When evaluated for CO2 capture, the adsorbent showed CO2 adsorption capacities of 5.97 mmol/g at 0 °C and 3.47 mmol/g at 25 °C, both at 1 bar. Adsorption isotherms were best described by the Sips model, indicating heterogeneous surface interactions. Correlation analysis revealed that CO2 uptake is predominantly influenced by micropore characteristics, particularly the narrow micropore volume, which exhibited a strong linear relationship, with R2 > 0.9 at 0 °C. Further analysis of the temperature-dependent adsorption behavior revealed that narrow micropores (<1 nm) act as the dominant adsorption sites, with the effective pore width narrowing from 0.33–0.82 nm at 0 °C to 0.33–0.72 nm at 25 °C. This reduction in effective pore width with increasing temperature limits the number of accessible adsorption sites, accounting for the observed decline in CO2 uptake. Moderate isosteric heats of adsorption confirmed physisorption, enabling facile regeneration. Furthermore, the activated carbons exhibited high CO2 uptake over N2 and excellent cyclic stability, demonstrating strong potential as sustainable adsorbents for CO2 capture.
Abstract The reservoir-on-a-chip (RoC) concept, built upon a microfluidics platform, enables real-time visualization of pore-scale flow dynamics, offering a distinct advantage over traditional core flooding. However, most RoC studies rely on idealized pore throat network models generated via Delaunay triangulation, which may not fully capture realistic flow behavior and volume-averaged metrics. This study benchmarks such networks against two alternatives─a physical rock network and an image-extracted pore network, by comparing flow dynamics, saturation evolution, and the volume averaged properties across all three configurations. The physical rock network was derived from Micronit Microtechnologies’ enhanced oil recovery chips. Two additional mathematical pore networks were constructed to simplify geometry: (i) an extracted pore network, derived directly from the physical rock network, and (ii) a statistical pore network, using the same pore locations and dimensions, while connecting throats were generated via Delaunay triangulation. All networks were simulated in COMSOL Multiphysics using the Navier–Stokes–Cahn–Hilliard system of equations to investigate pore-scale multiphase flow behavior and displacement dynamics. Numerical modeling reveals that the invading nonwetting fluid follows path of least resistance through the network, exhibiting both piston-like and concurrent displacement mechanisms. The model captures displacement instabilities characteristic of invasion percolation, along with pore-scale phenomena such as viscous fingering, and snap-off events, including Roof snap-off, Haines jumps, and fluid trapping. A trade-off analysis reveals that the physical rock network provides the most realistic representation of pore-level flow and volume-averaged properties, including recovery factor, Buckley–Leverett saturation history, and relative permeability curves, but requires an inordinately long time to converge. The statistically generated network accelerated convergence by 13 times but overestimated recovery by approximately 23% due to its idealized geometry and enhanced connectivity. The extracted pore network, reconstructed from the image data, achieved a practical balance by retaining key structural features while enabling faster simulation runtimes with minimal loss of accuracy in capturing displacement and saturation trends. These findings emphasize the importance of network selection and demonstrate the utility of the extracted network for scalable, physically grounded multiphase flow modeling.
Abstract Layered double hydroxides (LDHs) show great promise for electrochemical applications, yet their practical capacity is often constrained by severe nanosheet stacking and weak interlayer cohesion. Here, a hydrothermal strategy is employed to intercalate various molecules (l-aspartic acid, l-Asp; polyvinylpyrrolidone, PVP) and ions (MoO42–, SO32–, HPO42–) into ZnCo LDHs. XPS reveals that SO32– undergoes partial oxidation during synthesis to form mixed-valence sulfur (SO32–/SO42–). XRD and HRTEM confirm the coexistence of a secondary phosphate phase alongside the LDH host in the HPO42– system at higher concentrations. Despite these complexities, intercalation remains the dominant structural modification, with SOx2– enhancing charge compensation and the secondary phosphate phase in HPO42– only becoming significant at higher concentrations. Among all intercalated samples, ZC-SOx2–-2.0 exhibits the highest specific capacitance (272.94 F g–1 at 1 A g–1) with a rate capability of 72.85% at 20 A g–1, and the lowest charge-transfer resistance (0.044 Ω). This performance is attributed to modified interlayer chemistry and enhanced edge-site accessibility. The ZC-SOx2–-2.0//AC asymmetric supercapacitor device delivers an energy density of 17.77 Wh kg–1, and its practical applicability is demonstrated by two series-connected devices powering a red LED. All intercalated electrodes exhibit significantly improved cycling stability compared to pristine LDHs. This comparative study provides a rational basis for selecting intercalating species to optimize the electrochemical performance of LDH-based supercapacitors.
Abstract Efficient capture of low-concentration CO2 from combined cycle gas turbine (CCGT) power plant flue gas is challenging due to the high regeneration energy required in conventional chemical absorption. To address this issue, a novel low-energy carbon capture system was developed by integrating a biphasic absorbent with multiple process intensification strategies. Using an MEA-PZ-DEEA-H2O biphasic absorbent as the study target, a process model was established in Aspen Plus with the eNRTL thermodynamic model and a Rate-based mass transfer model, and validated using experimental data. A CCGT power plant with a treatment capacity of 45,000 N m3/h was used as a case study. Key operating parameters, including absorbent inlet temperature and stripper operating pressure, were optimized. The energy-saving potential of three process intensification strategies, absorber inter-cooling (AIC), rich solvent split (RSS), and mechanical vapor recompression (MVR), and their combinations was evaluated. The biphasic absorbent reduced regeneration energy consumption by approximately 21.5% compared with 30 wt % MEA. AIC and RSS alone reduced it to 3.00 GJ/t CO2 and 3.01 GJ/t CO2, respectively. Process coupling showed significant synergistic effects. The combination of AIC and RSS further decreased regeneration energy to 2.49 GJ/t CO2, representing reductions of 23.7% relative to the single biphasic absorbent system and 39.9% compared with MEA. Considering operational cost and engineering feasibility, the AIC + RSS process was identified as the most practical solution. This integration provides an efficient low-energy approach for capturing low-concentration CO2 from gas-fired power plants, significantly reducing system energy consumption and offering guidance for large-scale CCUS implementation.
Abstract Shale oil with low to medium thermal maturity (Ro = 0.5–0.9%) contains substantial residual hydrocarbon-generation potential but is difficult to exploit because of incomplete kerogen conversion, heavy hydrocarbon components, and restricted transport within nanoporous reservoirs. This review examines the integration of in situ conversion (ICP) with CO2-enhanced oil recovery and geological sequestration as a coordinated strategy for resource conversion, fluid mobilization, and carbon storage. ICP promotes kerogen pyrolysis and heavy-component cracking while inducing pore expansion, microfracture development, and changes in rock–fluid interfacial properties. These thermally reconstructed reservoir conditions subsequently regulate CO2 transport, phase behavior, oil displacement, and geological retention. CO2 enhances hydrocarbon recovery through oil swelling, viscosity reduction, compositional extraction, competitive adsorption, and diffusion-driven mass transfer, while geological storage occurs through adsorption, residual, dissolution, and mineral trapping. The coupled ICP–CO2 process is therefore interpreted within a thermo–hydro–mechanical–chemical (THMC) framework linking thermal conversion, pore-fracture evolution, multiphase transport, and long-term carbon sequestration. Published laboratory and core-scale studies indicate representative ICP heating temperatures of 300–450 °C, CO2 injection pressures of approximately 10–30 MPa, incremental oil recovery of 3–15%, and CO2 retention capacities of approximately 1–45 kg CO2 per ton of shale, although these values are strongly reservoir- and scale-dependent. Major uncertainties remain in nanoconfined CO2–oil phase behavior, cross-scale parameter upscaling, long-term reservoir integrity, and field validation. Future research should therefore integrate in situ experiments, multiscale THMC modeling, pilot testing, and full-cycle energy-carbon assessment to establish technically viable and low-carbon ICP–CO2 development strategies.
Abstract Hydrothermal experiments using rock and formation water at in situ conditions (100 °C, 50 MPa) were conducted for 60 days to evaluate geochemical processes after the introduction of either a strong acid (HCl) or a weak acid (H2CO3). The two experiments were designed to have equal initial pH values after injections. HCl was diluted and injected into the experiment with water because HCl is carried by other fluids when used in energy systems. H2CO3 was added to the experiment from CO2 injection because CO2 would be the injected fluid in the energy system. The experiments address the release and sequestration of strontium, manganese, nickel, and iron as pH and Eh evolve after acid injections. Both injections caused a decrease in pH, but pH returned to neutral values in less than 1 day after HCl injection. In contrast, the water remained acidic for the duration of the experiment after CO2 injection, which liberated aqueous metals. Carbonates dissolved after both injections, liberating strontium and manganese. Nickel and iron desorbed from clay surfaces after both injections as pH decreased. However, secondary precipitation of Fe(III)-oxyhydroxides was only observed in the CO2 injection experiment. The findings highlight contrasting geochemical behaviors after strong vs. weak acid injection and the implications of these behaviors for subsurface energy systems.
Abstract This study evaluates the potential for hydrate-based carbon dioxide (CO2) sequestration within Türkiye’s Exclusive Economic Zone (EEZ) in the Black Sea by mapping the CO2 Hydrate Stability Zone (CHSZ) and estimating storage capacities under different pore-water salinity conditions. CO2 hydrate equilibrium conditions were generated using the Hydrate Equilibrium Program (HEP), demonstrating that increasing salinity shifts hydrate stability toward higher pressures and reduces hydrate formation potential. CHSZ thickness maps were developed using spatial interpolation of hydrate stability data and revealed significant spatial variability, with the thickest hydrate stability zones occurring in deeper offshore regions. Monte Carlo simulations (5,000 realizations) were performed to quantify uncertainty in hydrate-based CO2 storage capacity using probabilistic distributions for key reservoir and hydrate parameters. For a pore-water salinity of 1 wt % sodium chloride (NaCl), the estimated storage capacity ranges from 587 MtCO2 (P90) to 2,111 MtCO2 (P10), with a median (P50) value of 1,154 MtCO2. Increasing salinity to 2 wt % substantially reduces the median storage capacity to approximately 125 MtCO2, highlighting the strong inhibitory effect of salinity on CO2 hydrate formation and stability. Sensitivity analyses indicate that sand fraction and hydrate saturation are the dominant controls on storage capacity uncertainty, followed by porosity. Comparison with current industrial emissions along the Turkish Black Sea coast suggests that the estimated offshore storage resource could accommodate decades of regional CO2 emissions under favorable conditions. The results demonstrate the significant potential of offshore hydrate-based carbon sequestration in the Black Sea while emphasizing the importance of accurate pore-water salinity characterization and site-specific investigations for future deployment.
Abstract The direct catalytic cracking of crude oil represents a promising strategy for increasing the production of high-value light olefins while enhancing carbon utilization in integrated crude-to-chemicals processes. In this work, the structure–activity relationships governing light olefin production over fluid catalytic cracking (FCC) catalysts containing nano- and microcrystalline ZSM-5 were systematically investigated using hydrocarbon gas condensate and Arabian crude oils as feedstocks. Nano-ZSM-5 catalysts with different silica-to-alumina ratios were synthesized and incorporated into FCC formulations to evaluate the combined effects of catalyst architecture, acidity, molecular diffusion, feedstock composition, reactor hydrodynamics, and hydrothermal stability on catalytic performance. The catalysts were comprehensively characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), nitrogen physisorption (BET surface area and BJH pore-size distribution), and ammonia temperature-programmed desorption (NH3-TPD) to establish correlations between physicochemical properties and catalytic behavior. The nanocrystalline catalyst possessing an intermediate silica-to-alumina ratio (FCC33) exhibited the highest catalytic performance, producing a propylene yield of 21 wt %, a total light olefin yield of 42 wt %, and the lowest coke formation during hydrocarbon gas condensate cracking. The enhanced performance was attributed to the synergistic interaction between optimized Brønsted acidity, increased external surface accessibility, improved pore connectivity, and shortened intracrystalline diffusion pathways, which promoted rapid β-scission while suppressing hydrogen-transfer reactions and coke precursor formation. Catalytic evaluation using Micro-Activity Test (MAT), Advanced Cracking Evaluation (ACE), and micro-downer unit (MDU) reactors demonstrated that reactor hydrodynamics significantly influence product selectivity, with the MDU providing the closest approximation to industrial FCC operation through its dilute catalyst phase, near plug-flow behavior, and extremely short catalyst–oil contact times. Feedstock composition strongly affected conversion and coke formation, with increasing crude oil aromaticity leading to lower cracking reactivity and higher coke yields. However, the optimized catalyst maintained high light olefin selectivity across the investigated feedstocks owing to its balanced acidity and enhanced molecular transport. Following severe hydrothermal aging at 810 °C for 6 h, the catalyst retained 87% conversion after 100 consecutive reaction–regeneration cycles, demonstrating excellent hydrothermal stability and regeneration durability under FCC-relevant conditions. These results establish that light olefin production during direct catalytic cracking of crude oils is governed by the coupled effects of the catalyst architecture, acidity, diffusion, feedstock composition, reactor hydrodynamics, and catalyst stability. The mechanistic insights developed in this work provide a rational basis for the design of next-generation FCC catalysts for high-severity crude-to-chemical applications.
Abstract Mitigating aviation’s carbon emissions remains challenging because air travel relies on energy-dense liquid fuels with limited substitutes. Here, we report a fermentation-based bioconversion process for producing isoprenol, a precursor to 1,4-dimethylcyclooctane (DMCO), a sustainable aviation fuel blendstock with Jet-A-comparable fuel properties and O-ring swelling behavior, which can substitute for aromatic additives and derived from lignocellulosic biomass at 25 °C. Ambient alkaline pretreatment achieved greater than 89% xylan deacetylation and 79–93% glucan digestibility across all feedstocks, without the formation of furan inhibitors. An engineered Escherichia coli strain directly fermented the unpurified biomass hydrolysate to isoprenol without requiring hydrolysate detoxification, demonstrating compatibility of the alkaline pretreatment stream with the fermentation step. The ambient pretreatment conditions produced no detectable furfural or HMF, enabling an isoprenol titer of 0.38 g/L (28 mg/g sugar consumed), comparable to pure sugar controls. This biochemical process is effective across corn stover, rice straw, and hemp hurd. This work establishes ambient alkaline pretreatment as a low-energy approach compatible with direct microbial isoprenol production across diverse feedstocks, providing a reduced-step route toward lignocellulose-derived sustainable aviation fuel.
Abstract Understanding the molecular structure of bio-oil is essential for improving upgrading strategies, predicting physicochemical properties, and designing efficient production pathways. This work introduces an integrated experimental-analytical-modeling framework that translates multimodal characterization data into large-scale, structure-resolved molecular representations of bio-oil. The approach combines elemental analysis, quantitative 13C NMR, GC-MS, FT-ICR MS/Orbitrap MS petroleomics, ESI(−)-MS molecular weight distribution, and bulk property measurements, including density and viscosity, to constrain the model composition and phase heterogeneity. A database of nonvolatile structures was generated using reactive molecular dynamics simulations and subsequently expanded through chemically consistent aging reactions, enabling broad coverage of experimentally observed molecular formulas. Two modeling strategies were evaluated: (i) treating the entire nonvolatile fraction as a single data set and (ii) using a subfraction-resolved formulation that incorporates the experimentally measured contributions of dehydrated sugars and pyrolytic lignin (dimer, trimers, tetramers, humins). Both approaches reproduced independent experimental constraints, including elemental composition, functional-group and molecular weight distributions, with errors below 10%. The resulting molecular ensembles captured key features of bio-oil behavior, including multiphase organization, micelle aggregation, and the role of hydrogen bonding in structural evolution. Additional validation through predicted 1H NMR and HSQC-NMR spectra showed strong agreement with experimentally observed chemical-shift regions, supporting the fidelity of the reconstructed molecular ensembles. This framework provides a chemically consistent pathway for resolving bio-oil complexity and generating predictive atomistic representations for downstream simulation and process-design applications.
Abstract Smoldering, as an emerging technology, exhibits significant potential for the efficient disposal of organic solid waste with high moisture content; however, theoretical models targeting multi-source blended fuels remain scarce. This work systematically investigates the smoldering characteristics and kinetic behaviors of municipal sludge (MS) and electroplating sludge (ES) under different airflow rates. The aim is to provide theoretical insights and model support for applying smoldering technology to various sludge feedstocks. An experimental smoldering reactor was constructed to examine the smoldering of both individual and blended sludges. Kinetic parameters were extracted using the smoldering isothermal fitting method (SIFM), and the activation energy asymptotic (AEA) simplified model was employed to predict and validate the smoldering temperatures of different sludges. The results demonstrate that MS and ES can achieve stable smoldering at specific blending ratios, thereby facilitating the synergistic co-disposal of multi-source sludges. As the MS proportion increases, the smoldering temperature rises and propagation stability is enhanced. Kinetic analysis reveals that the activation energy of blended sludge decreases with increasing MS content. When these parameters are input into the AEA model, the predicted results show good agreement with experimental data, with minor deviations under certain airflow conditions. Overall, the smoldering kinetic parameters obtained via SIFM are more suitable for the AEA model than those from non-isothermal thermogravimetric analysis (TGA), with deviations within ±6%. This agreement validates the model’s applicability to smoldering processes of different sludge types.
Abstract To address the bottlenecks of poor electrical conductivity in transition metal layered double hydroxides (LDHs) and the susceptibility of transition metal sulfides to structural degradation at high oxidation potentials, this work proposes an interface engineering and multi-component synergistic strategy. Through a two-step hydrothermal-sulfidation process a Co9S8/Ni3S2@NiFe-LDH composite electrocatalyst with a hierarchical “nanorod-nanoflower” heterostructure was successfully constructed. Experimental and characterization results indicate that this three-dimensional core–shell structure not only significantly increases the electrochemically active surface area but also induces strong interfacial electronic coupling that lowers the reaction energy barrier, accelerating charge transfer and reaction kinetics. Electrochemical measurements demonstrate that in a 1.0 M KOH electrolyte, the catalyst requires an overpotential of only 96 mV for the hydrogen evolution reaction (HER) with a Tafel slope of 88.77 mV dec–1 at a current density of 10 mA cm–2; for the oxygen evolution reaction (OER), the overpotential is 174 mV with a Tafel slope of 44.96 mV dec–1. In an alkaline seawater medium, the catalyst maintains excellent bifunctional activity, delivering HER and OER overpotentials of 108.5 mV and 153.5 mV, respectively, exhibiting good tolerance to ionic interference and structural stability. Overall water splitting tests reveal that the cell voltages required to achieve a current density of 10 mA cm–2 in alkaline and seawater systems are only 1.39 and 1.43 V, respectively, and the operating voltage remains highly stable during a 50 h durability test.
Abstract Silicon quantum dots (SiQDs) with an ultrasmall size and high specific surface area exhibit great application in enhanced oil recovery, especially in foam flooding. In this study, a series of amphiphilic silicon quantum dots (C3SPX-n) with tunable surface modification degrees were synthesized by using polyethylene glycol (PEG) and propyltrimethoxysilane (PTMS) as functional modifiers to enhance the foam stability of the nonionic surfactant PMIE. The chemical structure, surface composition, thermal stability, particle size distribution, and morphology of C3SPX-n were systematically characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Foam volume, foam half-life, film drainage half-life, Turbiscan Lab analysis, and microscopic foam morphology demonstrated that C3SP400-1.0 could more effectively enhance the stabilization of PMIE foam, even at a reduced surfactant concentration. Dynamic surface tension, wettability, and interfacial dilatational modulus measurements revealed that the 0.1% PMIE + C3SP400-1.0 system possessed superior interfacial adsorption behavior, improved surface viscoelasticity, and enhanced liquid film strength. The C3SP400-1.0-reinforced PMIE foam exhibited excellent tolerance under harsh reservoir conditions and efficiently increased crude oil recovery by 21.41% in sandpack flooding experiments. This work provides a new strategy for developing low-concentration, high-stability foam flooding systems and offers valuable guidance for achieving efficient water control and oil production enhancement.
Abstract High-temperature (>100 °C) operation of proton exchange membrane fuel cells simplifies water and thermal management, accelerates electrode kinetics, and improves impurity tolerance. However, the degradation mechanism of the membrane electrode assembly (MEA) under such conditions remains unclear. Here, a high-temperature-resistant MEA based on a phosphoric–sulfonic acid copolymer membrane is investigated through an accelerated stress test at 105 °C for 50 h. The initiation and propagation of crack networks within the cathode catalyst layer are identified as a critical bottleneck in performance degradation. Mass transport loss is the most pronounced degradation mode. This loss arises from crack formation, ionomer degradation, and carbon corrosion. The MEA exhibits a voltage decay of 35.23% at 2 A cm–2 and an electrochemical surface area loss of 62.9%. Chemically, cracks initiate from the transformation of disordered carbon into ordered carbon in the carbon support (ID/IG decreasing from 1.1268 to 0.4735) and the detachment of sulfonic acid side chains from the ionomer (I1060/I1210 decreasing from 0.483 to 0.133). Physically, Ostwald ripening of platinum particles (mean size increasing from 3.48 to 4.29 nm) and stress concentration induced by temperature and humidity cycling drive crack growth. Finite-element simulations using a cohesive zone model reveal that cracks propagate steadily along the ionomer/catalyst interface─the path of least energy dissipation. This study establishes a direct link from microstructural evolution to macroscopic performance degradation. Crack network formation is highlighted as a key bottleneck. These findings provide guidance for material design and lifetime prediction of high-temperature-resistant MEAs.
Abstract Converting CO2 into value-added carbon nanomaterials offers a compelling strategy for long-term carbon sequestration by generating commercially valuable products. Here, we demonstrate tandem plasma–thermocatalytic reactors for the coconversion of CO2 and C2H6 into carbon nanotubes (CNTs) and carbon nanofibers (CNFs). A dielectric barrier discharge plasma reactor activates a C2H6/CO2 feed mixture, generating reactive intermediates that serve as precursors for downstream thermocatalytic production of CNT over Co/Al2O3 at 750 °C and CNF over Co12K5/CeO2 at 450 °C. Systematic variation of plasma power and thermocatalytic reactor zone length reveals that these parameters strongly influence reactant conversion, product distribution, and carbon weight gain, enabling independent optimization of the plasma activation and thermocatalytic carbon growth. The tandem configuration enables CNT and CNF synthesis at lower temperatures than conventional chemical vapor deposition processes. An energy and CO2 footprint analysis demonstrates that, when powered by renewable electricity, the plasma–thermocatalytic system offers a modular, electrified pathway for carbon-negative sequestration. These results establish tandem plasma–thermocatalytic reactors as a flexible platform for reacting CO2 with light alkanes to produce carbon nanomaterials.
Abstract The sodium storage performance of hard carbon anodes is dependent on the precise modulation of their closed-pore architecture and surface chemistry. Herein, we propose a synergistic cross-linking strategy to synthesize nitrogen-doped hard carbon enriched with uniform closed-pore structure using polyvinyl chloride (PVC) and cellulose. During the solvothermal stage, urea not only serves as a nitrogen source but also facilitates the construction of a cross-linking network alongside ZnCl2-catalyzed dechlorination and depolymerization. Upon carbonization, the robust framework confines the in situ pore formation to a nanoscale domain with average diameter of ∼1.26 nm and preserves an expanded interlayer spacing of 0.401 nm. The optimized PZNC anode delivers a high reversible capacity of 359 mAh g–1 at 0.2 C and excellent cycling stability for 99% retention after 400 cycles at 1 C, maintaining 209 mAh g–1 after 1200 cycles at 5 C. The expanded interlayer spacing reduces Na+ diffusion resistance and the closed-pore structure enhance the low-voltage plateau capacity, enabling an efficient three-stage Na+ storage mechanism. This work provides a new pathway for designing advanced hard carbon anodes through integrating precise closed-pore engineering with chemical doping.
Abstract To meet the stringent durability requirements of proton exchange membrane fuel cells (PEMFCs) for heavy-duty applications, sealing reliability must be evaluated beyond the initial assembly state and linked to the long-term evolution of interfacial contact and gas-loss behavior. This mini-review focuses on gasket–MEA frame sealing interfaces in PEMFCs, with particular emphasis on flexible–flexible contact. It systematically examines recent progress in multiscale geometric characterization and reconstruction, constitutive and contact evolution under assembly and service loads, the competition between interfacial leakage and bulk material permeation, and the development of predictive modeling strategies from deterministic simulations to uncertainty-aware and data-assisted frameworks. The review highlights power spectral density (PSD)- and fractal-based surface reconstruction methods, discusses visco-hyperelastic and chemo-thermo-mechanical descriptions relevant to elastomer aging and contact-pressure retention, and clarifies that gas-loss behavior depends on a service-dependent transition between pressure-driven interfacial leakage and temperature-sensitive bulk permeation. It further summarizes multiscale transport modeling approaches involving slip-flow and Knudsen-scale effects, as well as recent advances in fluid–structure interaction, stochastic tolerance analysis, and surrogate-assisted prediction. Finally, the review outlines key future needs in lifecycle-oriented interface modeling, in situ experimental validation, benchmark data sets, and the integration of physics-informed machine learning with multiscale leakage prediction for health-state assessment and predictive maintenance of PEMFC stacks.
