Energy & Fuels最新文献

The accurate and fast simulation of CO₂ and n-alkane phase equilibria is crucial for guiding their industrial applications. We used Wang–Landau Transition-Matrix Monte Carlo (WL-TMMC) with the Free Energy and Advanced Sampling Simulation Toolkit (FEASST) software to compute the vapor–liquid equilibrium (VLE) of CO₂-methane and CO₂-hexane systems in both bulk and confined spaces. The bulk-phase simulation results were compared with literature data and constant volume Gibbs Ensemble (NVT-GEMC) results, with relative errors less than 6%. For confined systems, the results were compared with gauge cell grand-canonical Monte Carlo (gauge-GCMC) and pore–pore GEMC, with relative errors less than 8%. Notably, the WL-TMMC exhibits significant advantages in computing VLE for confined spaces. It requires only a single simulation to determine a pair of VLE points without being constrained by prespecified chemical potentials or pore geometry. Furthermore, the method provides free energy information for different fluid states, enabling the construction of a complete van der Waals loop from a single simulation. In conclusion, we demonstrate that WL-TMMC in FEASST is a robust and reliable tool for studying CO₂-n-alkane VLE.

The increasing demand for lithium-ion batteries (LIBs) capable of functioning in extreme environments underscores the limitations of conventional carbonate-based electrolytes, particularly at subzero temperatures. This study presents a nitrile-based electrolyte formulated with butyronitrile (BN), which offers an exceptionally low freezing point and high dielectric constant, critical for efficient lithium-ion transport at temperatures as low as −40 °C. The reductive behavior of BN in the presence of bis(fluorosulfonyl)imide (FSI) anions is effectively controlled by incorporating optimized concentrations of 1.5% vinylene carbonate (VC) and 10% fluoroethylene carbonate (FEC). Electrochemical testing reveals the optimized electrolyte achieves 145 mAh/g at C/20 and 105 mAh/g at C/1 at +25 °C, with minimal polarization and excellent capacity retention over 250 cycles. At −40 °C, the electrolyte retains 82.6% capacity at C/20 relative to room temperature, significantly outperforming conventional systems. Coulombic efficiency (CE) remains near 100% at room temperature and above 80% at −40 °C, emphasizing the stability of the passivation layer. Arrhenius analysis indicates lower activation energy, highlighting improved ion conduction under cryogenic conditions. This work demonstrates the critical role of passivating additives in forming a robust, ion-conductive solid-electrolyte interface (SEI), establishing the optimized 1.5% VC+10% FEC formulation as a transformative electrolyte composition for LIBs in aerospace, defense, and cold-climate applications.

To analyze the possible reasons that could cause organic waste to undergo self-heating and self-ignition, two fermentative wastes and chemical oxidation at low temperatures have been studied. Poultry waste and fecal matter were selected to observe whether these fermentative wastes behave differently from lignocellulosic wastes in the temperature range of 120–170 °C. The study suggests that the oxidation process and vapor sorption are similar to those of lignocellulosic materials, and simulations indicate that long periods, lasting many months or more, are required for self-ignition to occur at low temperatures. The oxidation of fresh grass has been studied over a wide temperature range, from 50 to 165 °C, revealing an increase in the heat evolved at low temperatures compared with what would be expected from the extrapolation of data obtained at high temperatures. Simulations suggest that self-ignition can occur after a relatively short period of time of approximately 1–4 days at low temperatures.

In the wellbore system of a CO₂ geological storage site, Portland cement is not adequately resistant to CO₂ corrosion. Therefore, it is essential to incorporate suitable additives that can hinder CO₂ corrosion in order to guarantee wellbore integrity. This study introduces supercritical CO₂-modified biochar (SCBC) as a wellbore cement additive, enabling wellbore cement to be resistant to CO₂ attack. Prior to exposure to CO₂, the samples were initially cured in 1 wt % of NaCl solution for 14 days under the conditions of 17 MPa and 62 °C, mimicking typical GCS conditions. Afterward, the samples were exposed to CO₂-saturated brine for 14 days, with the same pressure and temperature as the curing conditions. The performance of BC (BC with no supercritical CO₂ treatment) and SCBC samples to resist CO₂ attack and their influence on the hydration and strength of the wellbore cement were investigated and compared both with each other and with the control cement sample without BC (RF). The results indicate that SCBC demonstrates greater effectiveness in mitigating CO₂ corrosion (with a 30.97% inhibition efficiency of carbonation) when incorporated into wellbore cement, compared with the RF. This represents a 24.48% increase in the inhibition efficiency of carbonation compared to BC with no ScCO₂ modification. The compressive strength of the SCBC increased from 23.66 to 29.97 MPa, representing a 26.66% increase following 14 days of CO₂ exposure. In contrast, the compressive strength of RF decreased by 28.66%, while the compressive strength of BC with no ScCO₂ modification declined by 24.69% under the same conditions. The characterization results of the SCBC revealed two primary reinforcement mechanisms: (1) promoting the growth of calcite induced by carbonate formation within the cement matrix and (2) preventing CO₂ infiltration due to the preloaded CO₂ within the pores of the BC, along with its water-holding capacity, which aids in internal curing within the cement matrix.

Antimony halide perovskites have emerged as a potential alternative for lead halide perovskites in the fields of indoor photovoltaics, photodetectors, light-emitting diodes, and CO₂ photoreduction. Despite significant advances in device engineering, the fundamental properties and low-temperature dynamics of these materials remain unexplored. In this work, we have grown Cs₃Sb₂X₉ (X = Cl, Br, I) single crystals and investigated their low-temperature characteristics to gain insights into bonding interactions and lattice connectivity. Our findings show that changing the halide anion from X = Cl to Br and I can change their lattice connectivity and octahedral arrangement. Optical absorption spectroscopy, Raman spectroscopy, and other temperature-dependent measurements confirm lattice connectivity-driven photophysical properties in these lead-free perovskites. Additionally, low-temperature specific heat measurements reveal structurally dependent transitions within these crystals. The Debye–Einstein model was used to analyze the low-temperature heat capacity and observed low-frequency Einstein modes in all three crystals, generated from localized vibrations of Sb-X. These findings highlight the intricate relationship between lattice dimensionality and specific heat in antimony halide perovskites, providing insights into their fundamental properties and potential applications in a variety of fields.

To reveal the variation law of the microscopic remaining oil occurrence state under different displacement systems, this study carried out displacement simulation experiments using a micrometer CT scanning equipment. The experiments included continuous water flooding, water flooding converted to CO₂ flooding, and water flooding converted to polymer flooding. The occurrence state of microscopic remaining oil was quantitatively characterized at different displacement stages under different displacement systems. The results indicated that water flooding converted to CO₂ flooding and water flooding converted to polymer flooding could significantly improve the sweep efficiency, and the recovery rate increased by 13.6 and 5%, respectively, compared with continuous water flooding. Under the three displacement systems, with the progress of displacement, the average volume of remaining oil decreases continuously, the total number of remaining oil blocks increases continuously, the distribution of remaining oil becomes more and more dispersed, and the contact area ratio of remaining oil decreases continuously. Compared with continuous water flooding, the decrease degree of average volume of remaining oil, the increase degree of total number of remaining oil, and the contact area ratio reduction in water flooding converted to CO₂ flooding and water flooding converted to polymer flooding change obviously, but the change in the degree of water flooding converted to CO₂ flooding is the largest. During the displacement process, the cluster remaining oil is gradually converted to other types of remaining oil. The proportion of cluster remaining oil decreases, and the proportion of other types of remaining oil increases. The remaining oil in the residual oil state is mainly cluster, and other types of remaining oil coexist. The remaining oil occurrence types are highly dispersed in water flooding converted to CO₂ flooding and water flooding converted to polymer flooding.

The influence of water vapor (H₂O) volume fraction on the NO_x formation and reduction during MILD oxy-coal combustion (MILD-OCC) was investigated by using the plane diffusion flame pulverized coal combustion experimental system. The physicochemical effects of H₂O and CO₂ on NO_x formation during MILD-OCC were quantitatively separated by individually modifying the physicochemical properties of H₂O or CO₂. Numerical analysis was conducted on the effects of H₂O volume fraction on the combustion and NO_x formation characteristics under different coflow conditions during MILD-OCC. The results indicate that CO₂’s molar specific heat capacity is the main reason for the increased release time of volatile nitrogen. The effects of CO₂’s molar heat capacity and thermal conductivity are significant, delaying the volatile release time by approximately 38 and 11%, respectively. The dominant effects of H₂O’s thermal conductivity, radiative absorption coefficient, and mass diffusion coefficient of species in H₂O cause the combustion temperature to gradually decrease as H₂O volume fraction increases at 20%O₂. The gasification reaction weakens as the H₂O volume fraction increases under low-oxygen conditions, the endothermic reaction decreases, the combustion temperature rises, the CO concentration decreases, the NO_x reduction weakens, and the NO_x concentration gradually increases. The NO_x concentrations at 1473, 1673, and 1873 K decrease by approximately 12, 8, and 4%, respectively, when the H₂O volume fraction is increased from 0 to 40% at 20%O₂. Compared to the absence of H₂O, the NO_x concentrations at 10%O₂ and 5%O₂ with a 40% H₂O volume fraction increase by approximately 12 and 7%, respectively, at 1873 K.

Low-pressure nitrogen adsorption is a widely utilized experimental technique for evaluating the pore structure of coal with diameters between 0.35 and 300 nm. This work analyzes the effect of degassing temperature on nitrogen adsorption findings by analyzing low-rank coal from the Xishanyao Formation, employing low-pressure N₂ adsorption and nuclear magnetic resonance to evaluate pore structure parameters at different degassing temperatures. The findings reveal that the nanoscale pore geometry is predominantly defined by “ink bottle”-shaped pores, with micropores and small pores being the most common. Furthermore, the T₂ relaxation times display three unique peak spectra, underscoring the significant formation of micropores in the low-rank coal. Moreover, the structural fractal dimension (D₂₂) values for mesopores, spanning from 2.86 to 2.93, highlight the structural heterogeneity of the coal. NMR examination of the pore size and fluid states delineates five unique types of fractal dimensions: D_B, D_M, D_T, D_A, and D_S. The D_A for adsorption pores is notably below 2, signifying a lack of fractal properties. In contrast, D_B and D_T, denoting closed and total pores, respectively, demonstrate restricted fractal behavior within the closed pores. Nonetheless, high goodness-of-fit values for D_M and D_S in open and gas seepage pores suggest the existence of notable fractal characteristics. A negative association was observed between D_M, D_S, and the degassing temperature. The correlation study indicates that diminished fractal dimensions correlate with a more uniform pore distribution and enhanced pore connection, potentially improving coalbed methane production.

Nanoparticle (NP)-sized materials offer unique effects compared to their bulk counterparts and are widely utilized in perovskite solar cells (PSCs), contributing to a high-power conversion efficiency of approximately 27%. To improve further and achieve commercialization, issues related to PSCs, including limited absorption, lower stability compared to silicon solar cells, and optimization of morphology, must be addressed simultaneously. NP-based materials offer a solution to these problems. However, there are various types of NP, some of which are underutilized, and their roles are not well-understood. In this review, various types of NPs and their roles in the development of state-of-the-art PSCs are analyzed. In addition, a discussion and outlook on NP-based materials for future development of PSCs are carried out.

Circulating fluidized-bed flue gas desulfurization (CFB-FGD) is a widely employed semidry flue gas desulfurization technology due to its cost-effectiveness and easy operation. However, CFB-FGD cannot satisfy the ultralow emission requirement, particularly under high SO₂-containing flue gas conditions. This study aimed to enhance the CFB-FGD performance in a cost-effective way by regulating Ca(OH)₂ hygroscopicity in the desulfurization reaction. MgSO₄ was screened out from 7 hygroscopic additives. With a minor addition of 4.8 wt % MgSO₄, the sulfur capacity of Ca(OH)₂ increased significantly by over 15% compared to its pristine benchmark. By synthesizing structural characterization and DFT calculations, the pros and cons of the H₂O effect on the Ca(OH)₂ desulfurization reactivity were revealed and discussed from an atomic perspective. X-ray diffraction suggested that the introduction of water could activate the Ca(OH)₂ interlayer by expanding the interplanar distance in the (001) orientation, thus enhancing SO₂ adsorption. DFT calculations showed that the desulfurization reaction over Ca(OH)₂(001) was kinetically promoted in the presence of H₂O by facilitating proton transfer. By contrast, excessively high hygroscopicity was found to inhibit the desulfurization performance of Ca(OH)₂ by blocking porosity and hindering SO₂ diffusion by absorbing redundant moisture. This work demonstrated that tuning Ca(OH)₂ hygroscopicity is a low-cost and efficient way to boost SO₂ sorption, which advances Ca(OH)₂-based solution technologies for wider applications in the flue gas decontamination field.