Energy & Fuels最新文献

Conventional technologies primarily powered by fossil fuels have led to significant environmental issues. Hydrogen, which is a carbon-free fuel, has emerged as a substantial energy sector in recent years. However, challenges related to its storage and long-distance transportation remain obstacles to its widespread use. Conversely, with its superior energy density (12.9 MJ L^–1) compared to hydrogen (5.6 MJ L^–1), ammonia is more amenable to transport and offers a CO₂-free alternative that is versatile enough for various power generation systems. In this context, solid oxide fuel cell (SOFC) technology stands out as an effective solution for directly converting ammonia into electrical energy with high efficiency. However, the progress of this technology is hampered by the sluggish kinetics of the chemical and electrochemical processes occurring at the anodes and catalysts, limiting its commercialization. This review covers the fundamental principles, thermodynamics, and kinetics of the ammonia dissociation reaction, offering a comprehensive overview of how these factors influence the electrochemical performance and long-term durability of direct ammonia fuel cells at both the single-cell and stack levels. Furthermore, it provides critical insights for improving performance and mechanistic understanding while establishing a conceptual framework for the design of electrodes for ammonia-powered SOFC.

The facial tridentate N,N,O-donor ligand bpeH [1,1-di(pyridin-2-yl)ethanoate, L2] is based on the successful pyalkH [2-(2′-pyridyl)-2-propanoate, L1] ligand. L1 yields a precatalyst [Cp*Ir(pyalk)Cl] (1) that we have used extensively for water oxidation catalysis. We now find that L2 readily forms an Ir(III) water oxidation precatalyst, [Cp*Ir(bpe)]Cl (2) that can subsequently be chemically activated with sodium periodate to form a novel Ir(IV) water oxidation catalyst in the form of a blue solution species (BS2) analogous to the blue solution species (BS1) formed from 1. By optimizing the NaIO₄ stoichiometry in the activation process, a O₂ yield for water oxidation of 84% was achieved. A comparison of the activation of 1 and 2 showed that 2 yields a water oxidation catalyst with a higher O₂ yield. However, BS2 exhibited a 10-fold lower turnover frequency and reaction rate compared to BS1, likely because water molecules cannot access the positions trans to the μ-oxo ligand. This limitation causes BS2 to evolve into a more stable but less catalytically active molecular configuration. After O₂ evolution following the addition of NaIO₄ has ceased, BS2 reaches a quiescent state able to maintain its molecular integrity such that it can be reactivated with periodate even after 10 days under ambient conditions, restoring approximately 80% of the initial O₂ yield. Notably, minimal periodate addition was sufficient to reactivate the catalytic species. L2 further allowed the acquisition of the first clearly identifiable ¹H NMR spectrum of a blue solution. While the formation of paramagnetic species complicated complete NMR spectroscopic characterization, ongoing efforts are focused on elucidating the molecular structure of both the active and dormant species.

Low-temperature gas adsorption experiments are widely utilized to evaluate the pore structures of porous materials. Understanding the applicability of each model in different types of samples is crucial, as these models can yield diverse interpretations of pore structures from identical experimental data. In this study, low-temperature CO₂/N₂ isothermal adsorption experiments were conducted on coal, shale, and activated carbon samples to compare and analyze the suitability of each model in different samples and pore size ranges. The key findings are as follows. (1) Low-temperature CO₂/N₂ adsorption experiments provide insight into pore volume, specific surface area, and pore size distribution ranging from 0.36 to 160 nm in coal, shale, and activated carbon pores. (2) The CO₂-DFT model is applicable for analyzing the low-temperature CO₂ adsorption experiments in all samples. For the analysis of pores smaller than 35 nm in the low-temperature N₂ adsorption experiment, the slit hole nonlocal density functional theory model is recommended for middle-rank coal and the slit/cylindrical Quench Solid Density Functional Theory adsorption branch model for high-rank coal, shale, and activated carbon samples. For pore size larger than 35 nm, the Barrett–Joyner–Halenda model is recommended to analyzing the adsorption branches. (3) For overlapping pore interval of the different model’s analysis results, the CO₂-DFT model is recommended for the range of 1.41–1.47 nm, and the N₂-DFT model is recommended for the range of 4.14–36.00 nm.

The hydrate-based solidified natural gas technology offers a promising approach to the storage and transportation of natural gas. A key challenge of this technology is to achieve mild hydrate formation conditions and high gas storage capacity. In this work, the effects of temperature on THF-CH₄ hydrate formation under static conditions were investigated from multiple perspectives including kinetic measurement, thermal analysis, morphology observation, and in situ Raman spectroscopy. Moreover, the storage stability of THF-CH₄ hydrate above the freezing point was explored. The results indicate that 288.15 K is a preferable temperature for increasing the gas uptake of THF-CH₄ hydrate formation among the tested temperatures (280.15, 288.15, and 293.15 K), and the highest gas uptake of 0.0756 mol of gas/mol of water was achieved. The continued growth of cloud-like hydrates in the liquid phase was observed, which enhances CH₄ diffusion for further hydrate growth. In situ Raman spectroscopy measurement revealed a two-stage growth mechanism in the formation of THF-CH₄ hydrate. THF-CH₄ hydrate can be stably stored at atmospheric pressure and 277.15 K, with only a 3% gas evolution from the hydrate. The results presented in this work will provide valuable insights for improving the solidified natural gas storage and transportation technology.

The development of cost-effective and efficient adsorbents for CO₂ capture has gained significant interest, with biomass-derived porous carbon materials emerging as promising candidates due to their outstanding textural properties, tunable porosity, and low production cost. This study introduces for the first time a sustainable fabrication of porous carbon from Kraft lignin using K₂CO₃ as an environment-friendly activator via a spray drying approach and carbonization process. K₂CO₃ offers a low-toxic, low-corrosive, and eco-friendly alternative to KOH, making it safer for long-term equipment use and more suitable for large-scale applications. Furthermore, K₂CO₃ effectively creates a microporous structure for CO₂ adsorption while simplifying waste management due to its benign and recyclable carbonate residues. Unlike conventional two-step activation, our approach integrates carbonization and activation into a single step, reducing production time and enhancing efficiency, making it suitable for practical applications. Porous carbon materials obtained through this novel process exhibited a CO₂ adsorption capacity of 4.54 mmol/g at 298 K, comparable to those activated with KOH and outperforming many previously reported adsorbents. Additionally, the effects of K₂CO₃ concentration and carbonization temperature were systematically studied to optimize CO₂ adsorption performance. A linear correlation analysis between pore structure parameters and CO₂ captures highlighted ultramicropores as key contributors to adsorption efficiency.

Fuel additives play a significant role in improving combustion efficiency and fuel quality, with their surface tension being a crucial thermophysical property that directly affects atomization and cylinder performance. To address the demand for thermophysical data of fuel additives, 574 surface tension data for 22 fuel additives were extensively collected and evaluated using empirical models. A modified Sastri-Rao model (M-Sastri-Rao model) was built with critical temperature (T_c), reduced temperature (T_r), critical pressure (p_c), boiling point temperature (T_b), and acentric factor (ω) as influencing factors. The empirical models were found to have limited accuracy in predicting the surface tension. Then, a BP neural network model with the subtraction-average-based optimizer (SABO) algorithm was proposed. The results show that the SABO-BP model significantly reduced the deviation between calculated and experimental values, outperforming the previous empirical models. Various evaluation metrics were calculated for the SABO-BP model. The distribution of Bias ranged within ±5%, and the mean absolute error reached 0.165 mN·m^–1. The key parameters affecting the model were identified through a SHAP interpretability analysis. The SABO-BP model can accurately provide surface tension data for applications in the design and simulation.

Shale oil is mainly stored in the pores and cracks of mud shale reservoirs, which is the mainstream oil and gas resource development in the world today. Shale is a complex porous medium with low porosity and low permeability, which results in a short relaxation time of the nuclear magnetic resonance (NMR) signal. By characterizing the pore structure and fluid distribution of shale, one can effectively guide the exploration of shale oil. However, the NMR relaxation signal of shale decays so rapidly that it cannot be effectively characterized by conventional magnetic resonance imaging (MRI) methods. Zero echo time imaging (ZTE) is often used for imaging short T₂ tissues under high field conditions, where the theoretical value of the echo time (TE) of the pulse sequence is zero. In this study, the ZTE technique is implemented under low-field NMR, and the ZTE sequence is combined with relaxation NMR to obtain local information for shale samples before and after fluid self-absorption. The results show that ZTE technology can be applied to obtain high-quality shale images, and the heterogeneity of these samples was characterized. The fluid signals inside the samples were monitored, and the pore structure and fluid distribution inside the shale were characterized on macroscopic and microscopic scales. This method provides a trustworthy experimental technique for shale characterization and will benefit the oil industry.

To assess the potential for reducing carbon emissions, this study investigated the effects of fuel injection strategies, intake conditions, and engine speeds on combustion performance in ammonia–diesel dual-fuel engines. The results indicate that a high diesel injection pressure combined with advanced injection timing enhances the premixing of diesel and ammonia, shortens the ignition delay, and accelerates the combustion process, thereby improving the indicated thermal efficiency (ITE). Increasing the equivalence ratio reduces the compression pressure and temperature while decreasing the oxygen concentration around the diesel spray. This results in a longer ignition delay, a delayed combustion phase, and a combustion duration that initially shortens and then extends. Consequently, the ammonia combustion efficiency initially increases rapidly before gradually declining, while the ITE exhibits a similar trend, first increasing and then decreasing. At an ammonia energy fraction of 70%, the maximum ITE reaches 50.3%, representing an improvement of 6.7% compared with the pure diesel mode. At this point, the ammonia combustion efficiency is 94.6%, with NH₃ emissions of 14.5 g/kW·h, N₂O emissions of 0.17 g/kW·h, and NOx emissions of 2.9 times higher than the pure diesel mode. However, greenhouse gas (GHG) emissions are reduced by 67.5% compared with the pure diesel mode. Lower engine speeds of 1000 rpm result in lower greenhouse gas (GHG) emissions and ITE than 1500 rpm. Ammonia-fueled engines show promise in enhancing ITE and mitigating GHG emissions.

Aerobic oxidative desulfurization (AODS) is a promising technique for clean fuels production. Herein we present synergistic mixed carbide catalysts (FeMoWC) synthesized rapidly by microwave irradiation for AODS process. The combination of a ternary mixture of carbides for AODS leads to a significant increase in catalytic activity compared to single-phase, dicarbides or simply oxides of transition metals. The synthesized materials were characterized in detail by a complex of methods: XRD, HRTEM, EDX, SEM, XPS, low-temperature nitrogen adsorption/desorption, H₂-temperature-programmed reduction (TPR), Raman spectroscopy. Under selected conditions (150 °C, 6 atm, 0.5 wt % catalyst dosage) complete oxidation of dibenzothiophene (DBT) was achieved in just 20 min. Under optimal conditions, the specific catalytic activity was 12.73 and 293.43 mmol g^–1 h^–1 for the model and real fuel, respectively. A possible mechanism for the reaction is discussed, including the activation of atmospheric oxygen with the formation of a superoxide radical, the formation of alkyl peroxides and peroxo complexes. The proposed approaches open up wide possibilities for the future development of highly efficient AODS catalysts for practical application and production of clean motor fuels.

The development of low-cost, long-lasting, and high-performance bifunctional electrocatalysts is needed for effective electrochemical water splitting. Herein, an interface-boration engineering strategy was used to synthesize heterostructured nickel borate–nickel oxide (Ni₃(BO₃)₂–NiO) by using the electrospinning-incineration process, which exhibited an unprecedentedly high electrocatalytic activity in alkaline media. The Ni₃(BO₃)₂–NiO electrode showed ultralow oxygen evolution reaction and hydrogen evolution reaction overpotentials of 261 and 150 mV, respectively, to achieve 10 mA cm^–2. For Ni₃(BO₃)₂–NiO/NF-assisted alkaline as well as solar-driven electrolyzers, a low cell voltage of 1.60 V was needed to drive 10 mA cm^–2 and their catalytic activity was maintained for 40 h, indicating significant potential for their use in water-splitting. Ni₃(BO₃)₂–NiO was employed to generate H₂ effectively by consuming a power of 732.33 L_H2 kW h^–1 lower than that of cNiO (835 L_H2 kW h^–1). The enhanced adsorption of oxygen-containing Lewis base intermediates on Ni₃(BO₃)₂–NiO by Lewis acid–base interactions boosted the catalytic performance. This work provides a newer direction toward the rational engineering of the metal borate–metal oxide heterostructure with excellent intrinsic characteristics for energy applications, upscaled to industrial-scale H₂ production due to production simplicity.