Energy & Fuels最新文献

Graphene-based catalysts are emerging as promising alternatives to reduce reliance on metal-based catalysts in the hydrogen evolution reaction (HER). This study introduces a novel family of metal-free graphene-based materials codoped with nitrogen and phosphorus (GNP). These materials were synthesized, characterized, and evaluated for HER performance as glucose-tolerant cathodes for biomass electrolysis in a soft alkaline medium, referred to as Mixed Electrolyte (ME): 0.1 M NaOH + 1.0 M Na₂SO₄. It was found that the calcination time directly affects the catalytic properties of the final catalysts, with longer calcination times enhancing HER activity. This was attributed to the effective incorporation of nitrogen (N pyrrolic, N quaternary) and phosphorus (P graphitic) into the graphitic network, along with increased catalyst mesoporosity, which significantly improves mass and electron transfer. Furthermore, chronopotentiometry tests revealed substantial electrochemical activation of HER catalytic performance, stemming from the removal of heteroatoms from the carbon framework. This process, confirmed by XPS and Raman Spectroscopy, led to the formation of topological 5- and 7-membered carbon rings, which serve as the main active sites for the reaction. This significantly accelerates the water dissociation activity, leading to improved catalytic performance with a final overpotential (η₁₀) of −0.386 V in ME. Notably, the exceptional stability and electrochemical activity under various alkaline media, along with its tolerance in the presence of glucose, make this new cathodic catalyst a suitable candidate for a membrane-less biomass electrolyzer.

Kinetic hydrate inhibitors (KHIs) are primarily water-soluble polymers deployed in oil and natural gas production fields due to their remarkable performance in preventing gas hydrate formation at low doses. Unlike antiagglomerants and thermodynamic hydrate inhibitors, KHIs offer both technical and economic advantages as they are applicable to both high and low liquid loading systems and are not constrained by water cut limitations. However, most commercial KHIs are based on polyamides, which are incompatible with high temperatures and raise environmental concerns due to their nondegradable nature. Moreover, few KHIs are fit for inhibiting gas hydrates formed in a sour (H₂S) environment because of the challenge of both S–I and S–II hydrates potentially forming. We present a new class of KHIs, in which a synergist analogue has been incorporated into the polymer structure, and investigate their efficacy in inhibiting the formation of gas hydrates in a sour environment. These N-isopropylacrylamide and glycol ether copolymers were synthesized with varying molar ratios of monomers and molecular weights, and a comprehensive chemical and performance characterization was carried out. The copolymers exhibited excellent hydrate inhibition at low subcooling temperatures and at natural gas pressures of 100 bar, confirming their utility as effective KHIs for hydrates formed in sour environments.

During geological CO₂ storage, gravity segregation due to fluid density differences significantly affects the efficiency and safety of the process. This can result in premature CO₂ breakthrough, reduced storage efficiency, and increased leakage risks. This study aims to investigate how gas migrates in layered heterogeneous reservoirs over time due to prolonged density differences and to assess the resulting impact on fluid distribution. We use artificially layered heterogeneous sandstone cores for experimentation. After completing gas injection and water flooding experiments, the core was positioned with the low permeability layer (LPL) at the top and the high permeability layer (HPL) at the bottom for an extended period. Because the effects of density differences are not easily discernible during gas–water two-phase flow under typical driving forces, we applied micro-CT imaging technology to visualize and analyze how density differences influence gas flow within the core. The results demonstrate that during the static placement period following displacement, gas clusters exhibit different flow behaviors at the pore throats. Most gas clusters struggle to overcome the Jamin effect and enter into the upper pores; a few large-volume gas clusters, driven by density differences, partially pass through the throats into the upper pores, while the remaining portions are stranded within the throats, leading to a snap-off phenomenon; while some gas clusters successfully overcome the Jamin effect and enter the upper pores in significant numbers. The experimental findings indicate that the LPL effectively hinder the upward migration of the nonwetting phase gases from bottom and fluid density differences significantly influence gas–water distribution changes. This study provides critical insights for optimizing CO₂ storage and offers a new perspective on fluid behavior in layered heterogeneous reservoirs.

As a promising technology, aqueous zinc-ion batteries (ZIBs) represent a sustainable direction for future electrochemical energy storage systems. However, ZIBs have encountered a series of practical application problems, including the dissolution of the cathode material and sluggish kinetics, which eventuate rapid capacity decline and poor performance. In this study, we designed a novel cellulose separator modified by a hydrogen-bonded organic framework, which is called the FP/mHOF. FP/mHOF shows great performance, including suppressing capacity decay, boosting charge transfer kinetics, and mass transfer kinetics. FP/mHOF achieved stable cycling performance for 2000 cycles at the current density of 5 A g^–1 and 850 cycles at 2 A g^–1, whose capacity retention was up to 90.2 and 77.2%, respectively. As verified, HOF@FP shows great potential of being a next-generation separator for ZIBs.

Developing efficient and affordable electrocatalysts for the hydrogen evolution reaction (HER) is essential for advancing sustainable energy technologies. In this study, a high-performance covalent triazine-based framework supported Ag nanoparticle (CTF@Ag) was synthesized through a condensation reaction. The electrocatalyst was analyzed using Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nitrogen absorption and desorption analysis. The electrocatalytic behavior of the structures in HER was investigated by linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry in 0.5 M H₂SO₄. Results showed an onset overpotential of −46 mV (vs RHE), a low overpotential of −169 mV at a current density of 10 mA cm^–2, and a relatively high exchange current density of 0.37 mA/cm². The electrocatalytic activity of the CTF@Ag remained stable after 10 h, and even after 1000 consecutive cycles, the polarization curve characteristics were maintained, indicating the high stability of the electrocatalyst. The electrochemical analysis reveals that the synergistic effect between Ag nanoparticles and the CTF significantly improves the electron transfer. This work highlights the potential of CTF@Ag as a promising candidate for efficient hydrogen production through water splitting.

In this work, a detailed parametric study of sorption-enhanced methanation (SEM) to produce synthetic natural gas was carried out. A commercial Ni-based catalyst and CaO as a H₂O sorbent were used as functional materials. The operational parameters studied included the reaction temperature, H₂/CO module in the feed gas, CO space velocity, and sorbent/catalyst mass ratio. High CH₄ purity, close to 90%, was obtained at 275 °C, utilizing a module with H₂/CO = 3 as the feed gas, 0.8 kg_CO/kg_cat h, and a CaO/catalyst mass ratio of 1. Under these operational conditions, a cycle stability test was performed, demonstrating good reproducibility over 14 cycles. SEM performance was also analyzed using a sintered CaO sorbent. The study demonstrated that the reactivation of the material resulted in similar effectiveness to using calcined CaO. Finally, the process was studied utilizing a H₂/CO/CO₂ mixture as the feed gas, obtaining 80% CH₄ purity in the product gas.

Saline aquifers are prime candidates for carbon dioxide (CO₂) storage. However, some projects encounter challenges such as salt precipitation due to water evaporation during CO₂ injection. While salt precipitation alters reservoir porosity and permeability, the level of CO₂ injectivity remains higher compared to brine displacement using water-saturated CO₂. This study examines the effects of water-saturated (wet) and undersaturated (dry) supercritical CO₂ (scCO₂) injection on the properties of brine-saturated Stenlille sandstone reservoir cores from the Gassum Formation. Three high-volume core flooding experiments under reservoir conditions were conducted, analyzing dynamic differential pressure, in situ saturation changes (measured with a high-pressure acoustic separator), and pre- and postexperiment core properties. The results showed distinct differences between dry and wet CO₂ injection, particularly regarding the vaporization and salt precipitation effects on permeability. Dry CO₂ injection reduced water saturation to as low as 4% PV, simulating dry-out near injection wells, and caused absolute permeability changes of 21% on average due to salt precipitation. In contrast, wet CO₂ injection, representative of bulk reservoir flow, preserved high water saturations without salt precipitation. Additionally, the final relative permeability to supercritical CO₂ (Kr_scCO2) was higher for the dried core (0.62) compared to that of the wet injection experiment (0.40). This suggests that water vaporization during dry CO₂ injection enhances CO₂ effective permeability despite salt precipitation. Comparing wet CO₂ injections in samples with different permeabilities using dimensionless numbers revealed that unstable flow in high-permeability channels leads to higher overall relative permeability and residual water saturation. The comprehensive experimental data from this study provide valuable insights for simulating two-phase scCO₂–brine displacement and dissolution processes under reservoir conditions.

To evaluate sustainable aviation fuels (SAF) and other novel jet fuels, nontargeted comprehensive analysis by two-dimensional gas chromatography (GCxGC) is commonly utilized. The obtained results are necessary for subsequent model-based prescreening applications. The uncertainty of the respective property predictions is dependent on the degree of compositional detail as some properties (e.g., flash point, freezing point) are strongly influenced by structural molecular features. In the absence of sufficient structural reference data, individual identification from reference databases is usually not possible. Consequently, the results obtained from GCxGC are generally categorized by the carbon number and group type. To obtain greater details on the isomeric structure distribution of fuels, the iso-alkane family was further investigated. Therefore, a multilinear regression model for iso-alkane retention indices (RI) was constructed from molecular descriptors. Subsequently, the combined database from measurement and literature was extended by prediction to complete the data for all possible 42,900 branched isomers within the jet range (C7-C17). The isomeric structures were sorted into subgroups by their respective retention behavior, thereby correlating with the present number of molecular branches. The structural subgroup information was then used to create branching indicators to quantify and compare the subgroup distributions of different fuels. It was evident that isomeric distributions were unique to the respective samples. The new detail of composition will aid the characterization and differentiation of different fuels and present further potential for fuel assessment.

The complex pore size distribution and mechanical strength of rocks are critical parameters for characterizing unconventional energy development, fluid storage capacity, and resistance to failure. Low-field nuclear magnetic resonance (NMR) technology and uniaxial/triaxial loading failure tests are common methods for evaluating the pore structure and mechanical strength of rocks. The potential quantitative correlations among these parameters remain unclear due to the neglect of rock anisotropy and size effects. This study, grounded in nuclear magnetic relaxation and rock fracture mechanics theory, selected six types of rocks (φ25 mm × 50 mm) to analyze the relaxation-mechanics coupling responses. The relaxation parameters included total porosity (φ_NMR), T₂ geometric mean (T_2gm), and T₂ arithmetic mean (T_2am) for total pores, as well as T₂ geometric mean and T₂ arithmetic mean for effective free pores (corresponding to T_2gmf and T_2amf, respectively), while the mechanical parameters included compressive strength (σ_c) and elastic modulus (E). The results demonstrated that different rocks exhibited distinct relaxation and mechanical responses and φ_NMR, T_2gm, T_2am, T_2gmf, and T_2amf were negatively correlated with their respective mechanical parameters. These differences indicated that pore scale and connectivity largely determined both strength and relaxation, with the connectivity of large-scale pores providing numerous migration pathways for water. The accompanying relaxation time required for water-pore wall collisions became longer, while pore connectivity increased the relaxation amplitude. However, rock blocks with larger, connected pores generally exhibited lower strength and failure resistance due to the presence of numerous weak points. The different fittings were primarily influenced by pore size distribution, crack tortuosity, permeability, and capillary forces. Under confining stress conditions, nonlinear fittings emerged among relaxation, mechanics, and confining stress, indicating that confining stress exhibited significant sensitivity in the mechanics-relaxation coupling relationships. Confining stress positively influenced structural integrity, while pore/crack closure could negatively impact relaxation due to reduced water intrusion. The fitting variance of three-dimensional parameters demonstrated that different rocks exhibited varying crack surface roughness and stress sensitivity. These findings may positively contribute to data inversion between mechanical and relaxation responses using the same rock core, achieving multipurpose utilization of a single borehole in practical engineering applications.

Multiphase fluids are frequently encountered in numerous industries, yet there is a limited understanding of gas evolution behavior in these applications. Various physicochemical factors can impact the gas evolution rate from supersaturated solutions. Exploring the parameters that impact gas evolution is critical to better understand the gas evolution process. This study specifically focuses on elucidating the impact of pressure and oil concentration on gas evolution behavior. Exxsol D-110, a model oil, was used to investigate the impact of emulsion properties on the gas evolution rate. The research explored water-in-oil (W/O) and oil-in-water (O/W) emulsions to compare the gas evolution behavior across a concentration range using the same oil. In this work, stable emulsions were prepared to allow for mass transfer without any change to the droplet size distribution of the emulsions. In addition, surfactant concentrations were adjusted to facilitate the formation of stable emulsions. Span 80 was utilized as the surfactant to create stable W/O emulsions, while sodium dodecyl sulfate (SDS) was employed to produce stable O/W emulsions. The experimental pressure ranged from 500 to 1500 psia, while the oil phase concentration varied from 10 to 100%.