Energy & Fuels最新文献

Prescreening of sustainable aviation fuels (SAFs) is crucial for early stage development and ASTM D4054 evaluation. This study develops models to predict two key properties: temperature-dependent liquid density and surface tension of complex hydrocarbon mixtures. ¹H ¹³C heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy is used to determine atom type compositions. Multiple linear regression models, trained on 1241 liquid density and 1260 surface tension experimental data points, identified seven key atom types and a temperature-dependent term as predictors. Applied to fossil-derived and synthetic fuels, density predictions had an error range of 0.00-5.35%, and surface tension predictions ranged from 0.29-4.41%. The prescreening method proved to be effective for predicting critical fuel properties in early stage SAF development.

Understanding the kinetics of cation migration in hybrid perovskite materials is critical for enhancing their stability and performance in optoelectronic applications. This study investigates postsynthesis cation migration dynamics between 2D BA₂PbBr₄ and 3D MAPbBr₃ perovskite nanoparticles (NPs) in solution. Using in situ temperature-dependent photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM), we observed the formation of a quasi-2D intermediate phase (BA₂MAPb₂Br₇) resulting from interparticle cation exchange. The activation energy of the cation migration is measured to be 57 kJ/mol, and we associated this with the migration of methylammonium (MA⁺) ions, which migrate faster compared to the larger butylammonium (BA⁺) ions. This faster migration of MA⁺ is responsible for the formation of the quasi-2D phase, while BA⁺ ions migrate to the surface of 3D MAPbBr₃ NPs and efficiently passivate the surface defects, significantly enhancing the PL emission intensity and lifetime of the 3D MAPbBr₃ NPs. Furthermore, our study reveals that the reaction conditions, including temperature and the relative concentration of the 2D and 3D perovskite NPs, strongly influence the extent and dynamics of cation migration. Higher temperatures accelerate the migration process, as evidenced by the increasing intensity of the quasi-2D emission peak at 436 nm, while a higher concentration of BA₂PbBr₄ promotes the formation of the quasi-2D phase. TEM analysis confirms that the migration of MA⁺ ions into the 2D BA₂PbBr₄ lattice drives the formation of the quasi-2D structure, while BA⁺ ions predominantly passivate the 3D MAPbBr₃ surface. These findings provide mechanistic insights into interparticle cation migration and its impact on the optoelectronic properties of perovskite nanostructures, advancing their potential for stable device applications.

As the global demand for carbon reduction continues to grow, ammonia fuel, as a clean energy source, is gaining increasing attention. Against this backdrop, this study proposes an innovative integrated system that combines ammonia-fueled solid oxide fuel cells (SOFCs), a gas turbine (GT), and the Kalina cycle, aiming to achieve zero carbon emissions. Although there have been some similar studies primarily focusing on comparisons between different system configurations using the same fuel, this study is the first to integrate a pure ammonia system and compare it to traditional methane-fueled systems. To comprehensively assess the system’s performance, Aspen Plus software was used to develop a detailed process model, and both energy and exergy analyses were conducted. The results show that under the design conditions, the SOFC power generation efficiency is 52.5%, the overall system efficiency reaches 71.7%, and the total exergy efficiency is 67.3%. Further analysis reveals significant exergy losses in key components, such as the FC, afterburner, and GT. Additionally, the study delves into the impact of the fuel utilization coefficient and air utilization coefficient on system efficiency. The findings indicate that increasing the fuel utilization coefficient and reducing the air utilization coefficient can significantly enhance the overall system efficiency. Compared with traditional methane-fueled systems, the ammonia-fueled system demonstrates clear advantages in electrical efficiency, exergy efficiency, and zero carbon emissions.

Acidification is a commonly used chemical modification method to ameliorate the coal seam permeability. Current research on acidified coal mainly focuses on mineral composition, pore structure, and permeability. However, as one of the key stages of coalbed methane (CBM) development, there is still insufficient research on adsorption in acidified coal. The study selected HCl as the modification reagent and explored the pore and adsorption evolution characteristics through pore-combined testing technology and isothermal adsorption experiments. The results demonstrate that HCl acidification has a pore-enlarged effect on the macropore, with an increase in pore volume and a decrease in pore area. Mesopore displays pore-enlarged and transformed effect, with a decrease in pore volume and area. But HCl acidification has a weak effect on the micropore structure with chemical properties. The changes in the pore structure influence the Langmuir constant. Specifically, the decrease in macropore and mesopore area reduces the gas adsorption sites and weakens the adsorption capacity. The Langmuir constants generally show a decrease in Langmuir volume V_L and an increase in Langmuir pressure P_L. The study clarified the targeted control effect of HCl acidification on reducing coal adsorption and enhancing desorption efficiency and revealed the mechanism of CBM increasing production from the perspective of adsorption and desorption, which provides theoretical guidance and an evaluation basis for the HCl application in reservoir modification and CBM increasing production.

Current–voltage measurements are a standard testing protocol to determine the efficiency of any solar cell. However, perovskite solar cells display significant kinetic phenomena that modify the performance at several time scales, due to hysteresis, internal capacitances, and related mechanisms. Here, we develop a method to analyze the current–voltage curves by using large amplitude sinusoids as the excitation waveforms, specifically addressed to determine the influence of cycling frequency on relevant performance parameters. We solve a system of equations representative of charge collection and recombination, that provide the frequency-dependent dynamical behavior of the internal ion-controlled surface recombination processes that cause open-circuit voltage variations often observed in high performance devices. We analyze several reported experimental data pertaining to state-of-art devices, and we showcase the key parameters governing the evolution of hysteresis phenomena as the scan speed is increased in relation to Impedance Spectroscopy.

To elucidate the effects of fluid viscosity and stress on the characteristics of hydraulic fractures, a series of triaxial laboratory experiments were performed on continental shale using water and supercritical CO₂ (Sc-CO₂). Utilizing advanced computed tomography scanning and three-dimensional reconstruction techniques, we quantitatively assessed the fractal dimension, connectivity, and volume of the induced hydraulic fractures. To provide a rigorous quantitative evaluation of the hydraulic fracturing effectiveness, we introduced a novel comprehensive fracturing index (CFI). Our experimental results reveal that the bedding planes of the Chang7₃ Formation continental shale significantly influence the morphology of hydraulic fractures. Under consistent differential stress conditions, Sc-CO₂ preferentially initiates fractures along the bedding planes, exhibiting limited vertical propagation. Notably, a higher differential stress is required to promote vertical propagation of the fractures, with approximately 30 MPa necessary for Sc-CO₂ in this study to induce vertical propagation. This study represents the first detailed analysis of the fracturing performance of continental shale under various confining pressures using Sc-CO₂. At a confining pressure of 20 MPa, the height of hydraulic fractures was only 14.5% of that observed without a confining pressure under the same differential stress. Through the application of the proposed CFI, we observed that, under identical differential stress conditions, the CFI for Sc-CO₂ fracturing was lower compared to that for water fracturing. With increasing differential stress, the CFI for water-based fracturing exhibited an initial increase, followed by a decrease. When the differential stress was sufficiently high to make fractures to propagate vertically, the complexity of the fracture morphology induced by Sc-CO₂ increased significantly, leading to a notable rise in CFI. This research provides critical empirical insights for the selection of fracturing fluids and the optimization of fracturing techniques for continental shale formations.

Prescreening of sustainable aviation fuels (SAFs) is crucial for early stage development and ASTM D4054 evaluation. This study develops models to predict two key properties: temperature-dependent liquid density and surface tension of complex hydrocarbon mixtures. ¹H ¹³C heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy is used to determine atom type compositions. Multiple linear regression models, trained on 1241 liquid density and 1260 surface tension experimental data points, identified seven key atom types and a temperature-dependent term as predictors. Applied to fossil-derived and synthetic fuels, density predictions had an error range of 0.00–5.35%, and surface tension predictions ranged from 0.29–4.41%. The prescreening method proved to be effective for predicting critical fuel properties in early stage SAF development.

The design of new lithium-ion battery cathode materials must balance many factors: performance, cost, manufacturability, safety, critical mineral usage, and geopolitical constraints. Recently, commercialized LiMn_xFe_1–xPO₄ (LMFP) materials offer good energy density and stability, low material cost, and excellent safety characteristics, avoiding the use of Co or Ni. Within this material set lies a wide variety of potential formulations (Mn/Fe ratio) exhibiting varied cathode properties and challenges. In this work, we assessed three commercially available LMFP materials with Mn content in the range of 60–80% in full cell format, confirming the role of the Mn/Fe ratio on specific capacity, energy density, and electrochemical stability. High Mn content increased the average discharge voltage while maintaining specific discharge capacity, with 80% Mn providing an 18% boost to initial gravimetric energy density over LFP. However, worse kinetics and increased capacity fade rate resulted in the reduction and eventual elimination of this energy density advantage after 100 cycles. A blend cathode (LMFP and LiNi_0.8Mn_0.1Co_0.1O2, NMC811) was also evaluated, exhibiting characteristics of both material types. An initial 23% boost to energy density over LMFP alone was diluted following NMC-dominated degradation in early cycles, but enhanced capacity retention over NMC811 alone remained in long-term cycling. This work highlights the potential advantages of these newly commercialized materials while identifying outstanding challenges to widespread adoption and exploitation.

In order to clarify the effect of deuterium water huff-n-puff (D₂O HnP), carbon dioxide huff-n-puff (CO₂ HnP) and CO₂ HnP after D₂O HnP (CAD HnP) on the production characteristics of crude oil in shale micro-nanopores, the microscopic space and pore connectivity of shale reservoir were characterized by scanning electron microscopy, high-pressure mercury injection, and shale spontaneous imbibition experiment. The NMR and MRI experiments of D₂O HnP/CO₂ HnP were carried out to study the effects of different huff-n-puff media enhancing oil recovery in shale pores from the microscopic scale. It was determined that the pore diameter distribution range of the target shale reservoir was wide (2 nm ∼ 10 μm), the slope of spontaneous imbibition curve was small, and the pore connectivity was general. The recovery degrees of D₂O HnP, CO₂ HnP, and CAD HnP were 20.16, 36.81, and 39.41%, respectively. The oil recovery degree of CAD HnP in large pores (r > 20 nm) and small pores (r ≤ 20 nm) reached 31.86 and 7.55%, respectively. With the increase of huff-n-puff rounds, the recovery degree of a single round gradually decreased. Combined with MRI, the utilization of shale oil developed by CAD HnP was clarified. In the initial stage of matrix shale, water and CO₂ mainly used crude oil in the surrounding area of the core. With the increase in the number of CO₂ HnP rounds, the crude oil inside the core was gradually utilized through CO₂ diffusion. Prolonging the huff-n-puff rounds and soaking time appropriately could improve the CAD HnP recovery. The CAD HnP method of injecting water for 1 round and CO₂ for 2 rounds was a better way to development. The preferred soaking time was 24 h for laboratory experiment. The research results could provide some reference and guidance for the field test of water, CO₂, and CAD HnP.

Hydrogen represents a promising clean energy; however, the application of hydrogen energy is limited by the prohibitively expensive commercial Pt/C catalyst for the hydrogen evolution reaction (HER). In this work, we designed non-noble high entropy alloy (HEA) catalysts of FeCoNiCuMo with diversified active centers, which have an excellent catalytic performance for HER. Density functional theory calculations indicate that Fe, Co, and Ni sites with strong adsorption of H* could facilitate water splitting, while Cu and Mo sites with weak adsorption of H* could promote the formation of H₂. As a proof of concept, we synthesized nanoporous (NP) FeCoNiCuMo by ball milling and dealloying to further increase the designed active centers, resulting in an onset potential of 0 V vs reversible hydrogen electrode (RHE) and overpotential of 68 mV at −10 mA cm^–2, which are even comparable to that of the Pt/C catalyst. Our work highlights the great potential of NP non-noble HEA catalysts for HER and accelerates the industrial application of hydrogen energy.