Korean Journal of Chemical Engineering最新文献

We propose a universal surface reaction model that incorporates neutral and ion transport mechanisms through a steady-state passivation layer in high-aspect-ratio plasma oxide etching. This two-layer model effectively captures the concurrent deposition and etching characteristics by explicitly accounting for neutral diffusion and ion scattering transport processes. Detailed kinetic models for deposition and etching are developed to closely reflect the transport mechanisms in a steady-state passivation layer (SSPL), and their validity is supported by sensitivity analyses of key parameters against experimental data. Consequently, the proposed model provides a realistic description of plasma oxide etching behavior. Furthermore, by integrating this model with a well-established three-dimensional ballistic transport model in high-aspect-ratio (HAR) structures, we offer valuable insights into previously unexplored aspects of the HAR etching process.

Nickel–Zinc (Ni–Zn) batteries are attractive as a potential alternative to conventional lithium-ion batteries due to their cost-effectiveness and environmental benefits. This study explores the fabrication of a flexible electrode using nickel hydroxide (Ni(OH)₂) that is electrochemically deposited on a Buckypaper and polydimethylsiloxane (BP@PDMS) substrate. The electrodeposition condition is optimized by varying applied current density (− 1, − 1.5, and − 2 mA/cm²), and − 1.5 mA/cm² condition yields the highest specific capacity of 0.2 mAh/cm². According to spectroscopic and optical analyses, when − 1.5 mA/cm² is applied, Ni(OH)₂ is properly deposited on the BP@PDMS electrode, inducing a high specific capacity. Furthermore, Ni(OH)₂/BP@PDMS cathode is compared with (i) Ni foil cathode, and (ii) untreated BP@PDMS cathode to demonstrate its superior redox reaction, capacity, and stability. Despite minor capacity decay of Ni–Zn battery occurring for a long cycle test, the findings suggest that Ni–Zn batteries are suitable for portable electronic devices and offer a promising alternative to existing battery technologies.

Developing highly active and durable catalysts to reduce iridium (Ir) usage for the oxygen evolution reaction (OER) is essential for cost-effective hydrogen production via polymer electrolyte membrane water electrolysis (PEMWE). Herein, we report copper–iridium nanotubes (Cu–Ir NTs) with an ultrathin 2 nm Ir layer for OER, synthesized through a three-step process: (1) formation of Cu nanowire templates, (2) deposition of an Ir shell layer, and (3) partial removal of the Cu nanowire templates via an acid treatment. X-ray photoelectron spectroscopy analysis reveals strong electronic interactions between Cu and Ir, altering the adsorption energy of oxygen intermediates on Ir surface. Furthermore, the Cu–Ir NTs possess a high electrochemical surface area (ECSA) of 61.9 m²/g, nearly twice as large as Ir black (30.7 m²/g), due to an obtained 1-dimensional hollow structure. These synergetic effects result in outstanding OER mass activity (504 A/g) and specific activity (8.1 A/cm²) of the Cu–Ir NTs in acidic media, significantly surpassing Ir black (200 A/g, 6.5 A/cm²). Additionally, the Cu–Ir NTs demonstrate an extended operating time in chronopotentiometry experiment at 10 mA/cm². These findings highlight the potential of the Cu–Ir NTs as cost-effective and high-performance OER catalysts for PEMWE.

Based on empirical data from a commercial on-site hydrogen refueling station, this study quantitatively analyzes the system’s energy consumption structure and the root causes of its inefficiency. The analysis revealed that while the share of total energy consumption was highest in the order of production (51.0%), compression (36.3%), and dispensing (12.7%), the contribution to overall inefficiency, as measured by Specific Energy Consumption (SEC), showed a different distribution: production (35.9%), compression (28.9%), and dispensing (35.2%). Notably, the dispensing process, despite being the smallest total energy consumer, was a primary source of the system’s overall energy inefficiency, revealing a significant structural problem. The inefficiency in the production process was primarily caused by performance degradation under low-load conditions, whereas the dispensing process’s inefficiency stemmed from substantial standby power losses from its continuously operating chiller. These findings quantitatively demonstrate that a mismatch between operating conditions and actual demand is the most fundamental problem degrading the efficiency of the on-site hydrogen refueling station.

Lithium-ion batteries dominate the landscape of electrochemical energy storage, driving research on sodium-ion batteries to focus on enhancing sustainability and cost-effectiveness through the innovation of advanced electrode materials. In this study, chlorine-doped graphene oxide (ClGO) powders were synthesized as an anode Material for sodium-ion batteries using a straightforward one-step chronoamperometric method. The morphology of the as-prepared sample has been investigated by scanning electron microscopy and transmission electron microscopy. XRD shows that the interlayer distance was increased due to chlorine doping, with an averaged spacing around 0.67 nm of the plane (002). The charge/discharge curves show initial specific discharge capacity of 389.7 mAh.g⁻¹ at a current rate of 0.1 C. X-ray photoelectron spectroscopy measurements indicate that the powder surface is covalently doped by C–Cl formation. Doping also led to the formation of Cl-containing oxygenated groups –ClO_x, (x = 2, 3, 4). Meanwhile, Raman spectroscopy showed that the synthesized powder had double layers with nanocrystalline domain size (Lα) ~ 49 nm, and the number of sp² carbon rings was calculated to be ~ 19. The diffusion coefficient for ClGO determined through electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) measurements, was found to range between 10^–13 and 10^–10 cm² s⁻¹. Besides, the capacity retention for long-term cycling of 100 cycles at 2C rate was ~ 100%. The results show that this ClGO synthesis method presents a promising approach for developing potential, feasible, and tunable carbon-based anodes for Na-ion batteries.

Graphical Abstract

Glucose oxidase (GOx)-based electrodes offer promising applications in glucose sensing and as potential power sources for implantable devices, yet their performance remains critically dependent on efficient electron transfer and enzyme immobilization strategies. This study systematically investigated the co-immobilization of GOx and a redox-active osmium polymer, poly (N-vinylimidazole)-[Os(4,4′-dimethyl-2,2′-bipyridine)₂Cl])^+/2+ (PVI-Os-dme), using poly(ethylene glycol) diglycidyl ether (PEGDGE) as a crosslinker to enhance both the catalytic and electron-transfer properties of the electrode. By varying the enzyme-to-mediator ratio and applying a layer-by-layer assembly approach, we demonstrated that both loading quantity and composition critically influenced current generation, charge transfer resistance, and overall electrode efficiency. While current output increased with additional layers, the catalytic activity per unit mass of enzyme or mediator decreased, indicating a trade-off at high loadings. The optimized electrode, composed of six composite layers (2 μg GOx, 3.6 μg PVI-Os-dme, 2.2 μg PEGDGE per layer), achieved the highest peak current of 23.7 ± 1.7 μA at 0.3 V and retained over 85% of initial current after 3 cycles and 57% after 5 cycles, demonstrating favorable reusability. Kinetic analysis revealed an apparent Michaelis–Menten constant (K_m^app) of 9.0 mM and a maximum current (I_max) of 29.2 μA, confirming the electrode’s high affinity and catalytic efficiency toward glucose. These results highlight the importance of optimizing GOx/PVI-Os-dme loadings, ratio, and the number of layers for enhancing the electrode performance.

The process of refueling Hydrogen Fuel Cell Electric Vehicles (HFCEVs) with compressed hydrogen gas faces two primary challenges: the temperature rise in the vehicle tank and delay in fueling speed. Since most Hydrogen Refueling Stations (HRSs) are addressing these challenges through cascade systems, there is a demand for performance evaluations of fueling systems under various HRS configurations and operating conditions. However, there is a lack of generalized and validated simulation codes, and experimental results are quite limited. In this study, we develop a model that can simulate real-world fueling processes, including the cascade system, and conduct case studies based on actual HRS configurations. By implementing a more detailed mathematical model than previous studies and simulation code for not only light-duty vehicles but also heavy-duty vehicles, the developed model accurately and extensively simulates the fueling process for various operating conditions and diverse types of vehicle tanks. The reliability of the developed model is validated using real-world data collected from operational HRSs, including extreme operating conditions. The implemented code is available as open-source and supports developing the configuration and operation guidelines of HRSs to be built forward or running now.

We present a novel sequential experimental design framework that combines the interpretability of classical response surface methodology with the adaptability of Bayesian optimization. At each iteration, a second-order polynomial surrogate model is refitted and the next experiment is selected using a variance-weighted curvature (VWC) acquisition function that targets locations where the surrogate is uncertain and/or strongly curved. Sampling in these information-rich regions can improve global model fidelity while still revealing optima. Through three benchmark problems—including a five-dimensional sparse quadratic and a non-quadratic surface—the VWC criterion achieves one to three orders of magnitude lower prediction error than Gaussian process-based Bayesian optimization while requiring significantly less computation. The proposed framework is fast, interpretable, and readily scalable, making it well suited to data-intensive experimentation in chemical engineering and related fields.

Carbon dioxide (CO₂) methanation, also known as the Sabatier reaction, is a promising strategy for mitigating greenhouse gas emissions while enabling the storage of renewable hydrogen in the form of methane. However, achieving high catalytic activity, selectivity, and long-term stability under industrially relevant conditions requires the development of catalysts with tailored structural and functional properties. Conventional catalysts based on Ni, Ru, and Rh have demonstrated considerable performance in CO₂ methanation. Nevertheless, challenges associated with high-temperature catalysis such as thermal degradation, carbon deposition (coking), and the high cost of noble metals still remain. To address these issues, oxide-type materials have attracted increasing attention due to their multifunctional roles not only as catalyst supports but also as active materials in the catalytic process. Simple oxides such as Al₂O₃, SiO₂, CeO₂, and ZrO₂, as well as more structurally complex oxides such as perovskites (e.g., LaNiO₃, SrTiO₃) and spinels (e.g., MgAl₂O₄), can significantly influence metal dispersion, reducibility, and metal–support interaction strength. As a result, these characteristics critically affect both catalytic performance and durability of CO₂ methanation. Moreover, many oxides actively participate in the reaction mechanism by facilitating oxygen vacancy formation, hydrogen spillover, and dynamic redox behavior, making them essential components in the design of next-generation CO₂ methanation catalysts. This review summarizes recent progress in oxide-type materials for catalytic CO₂ methanation and highlights material design strategies aimed at developing catalysts with high activity, selectivity, and durability.

Solvent extraction is a broadly employed method for removing impurities from wet-process phosphoric acid (WPA). However, the raffinate acid generated by this method remains underutilized due to its high viscosity and elevated metal impurity (Fe, Al, Mg) content and nonmetallic impurities (S, F), resulting in resource waste. This study employs P-15 as the extractant to purify raffinate acid and introduces an innovative stripping–crystallization process for the separation and recovery of Al³⁺ and Mg²⁺, yielding high-value products. A comparative analysis of various stripping agents identified a sulfuric acid solution containing ammonium sulfate as the optimal system. Under the optimized conditions (temperature: 303.15 K, organic–aqueous phase ratio (O/A): 1:1, sulfuric acid concentration: 30 wt.%, reaction time: 30 min), the stripping efficiency reached its optimal value. Theoretical stage calculations using the McCabe–Thiele method and cascade simulation determined that a two-stage countercurrent operation is required. To address crystallization inhibition caused by aluminum–fluoride complexes, silicon or boron (introduced as sodium silicate or borax) was incorporated to form more stable SiF₆²⁻or BF₄^- complexes, facilitating Al³⁺ release and its subsequent precipitation as NH₄Al(SO₄)₂·12H₂O. Further addition of ammonium sulfate enabled the formation of (NH₄)₂Mg(SO₄)₂·6H₂O. This study provides an efficient and environmentally friendly process for the valorization of raffinate acid from WPA production, offering significant industrial application potential and environmental benefits.