Korean Journal of Chemical Engineering最新文献

Aqueous organic redox flow batteries (AORFBs) attract a significant attention for large-scale energy storage systems owing to their intrinsic safety, low cost, and design flexibility. Among various organic redox couples, 2-hydroxy-1,4-naphthoquinone (Lawsone) and ferrocyanide (FeCN) combination exhibits a promising electrochemical performance. However, its practical application is hindered by capacity decay arising from side reactions occurring under strongly alkaline conditions. Although chemical modification of Lawsone proposes to improve cycling stability, such approaches generally require complex synthesis and increase material cost. In this work, supporting electrolyte composition is adjusted to alleviate the strongly alkaline environment without modifying the active material. Specifically, hydroxide is partially replaced with chloride to reduce alkalinity of electrolyte and the effects of potassium salt anions on electrochemical behavior and battery performance of Lawsone anolyte is investigated. Contrary to the initial expectation, conventional 1 M KOH electrolyte exhibits superior electrochemical kinetics, leading to higher capacity utilization and improved cycling stability than the mixed electrolyte (0.8 M KCl + 0.2 M KOH). AORFB employing 1 M KOH retains 72% of its initial capacity after 100 cycles, whereas mixed electrolyte preserves only 42%. These findings indicate that electrochemical performance is governed not only by electrolyte alkalinity but also by the nature of supporting electrolyte anion.

Black-silicon (b-Si) nanowire photocathodes provide excellent light trapping; however, their high-area interfaces frequently accelerate charge recombination and photocorrosion during photoelectrochemical (PEC) hydrogen evolution in strong acid. We present a multifunctional thermal TiN-centered interfacial engineering approach for fabricating p-Si (100)-based nanowire photocathodes, enhancing the PEC water-splitting efficiency for solar hydrogen production. TiN was selected as the interfacial layer because it combines electrical conductivity, conformal ALD growth, chemical robustness, and protective passivation, thereby addressing the limitations of insulating oxide-based protection layers. An ultrathin TiN layer deposited by thermal atomic layer deposition (ALD) acts as a conductive passivation/protection structure, facilitating the durable incorporation of a solution-processed MoS_x co-catalyst (derived from (NH₄)₂MoS₄) and sparsely distributed Pt nanoparticles. A systematic TiN thickness series (3 to15 nm) identifies 5 nm as an optimal window, increasing the photocurrent at 0 V vs. RHE from − 0.143 mA cm^− 2 for bare b-Si to -0.288 mA cm^− 2 after TiN passivation. Following MoSₓ functionalization and the electrodeposition of a small amount of Pt, the optimized photocathode achieves a photocurrent density of -3.7 mA cm^− 2 at 0 V vs. RHE and shows significantly improved photocurrent retention over 6 h of operation in a harsh acidic electrolyte. This study reveals that the conformal 5 nm TiN interlayer acts as a critical multifunctional platform, simultaneously providing efficient charge extraction, effective surface passivation, and robust chemical protection against acid corrosion. This nanoscale interface engineering strategy effectively separates surface passivation from catalytic activity, overcoming the conventional trade-off between optical transparency and long-term chemical durability in silicon-based PEC photocathodes.

As Hydrogen Fuel Cell Electric Vehicles (HFCEVs) expand, accurate prediction of the entire refueling process is essential for improving refueling protocols and station operation. This study proposes a Physics-Informed Hybrid Modeling Framework that combines thermodynamic interpretability with data-driven calibration. The framework consists of five sub-models for supply pressure, flow rate, supply temperature, tank temperature, and tank pressure, preserving governing-equation structures while automatically calibrating 24 empirical parameters using Bayesian optimization. Approximately 32 months of operational data from a commercial hydrogen refueling station were used, with 4,943 training scenarios for parameter calibration and 4,943 validation scenarios for Initial Value Problem (IVP)-based prediction. The framework consistently reproduced refueling behavior across all sub-models, showing particularly high accuracy for supply pressure, tank temperature, and tank pressure. These results demonstrate its potential as a practical simulation tool for optimizing station operation and designing high-speed refueling strategies.

Polylactic acid (PLA) was developed as a biodegradable alternative to fossil-based plastics. However, practical disposal method for PLA has not yet been established. To address this, the present study proposes hydrothermal liquefaction (HTL) as a strategy for valorizing PLA into energy resources (biocrude). Spent coffee grounds (SCG), which are rich in lipids, were employed as a co-feedstock to enhance biocrude quality. The optimal operating conditions for maximizing biocrude yield were explored by adjusting various operating parameters, including the PLA-to-SCG mass ratio, a reaction temperature, a reaction time, a water-to-feedstock (W/F) ratio, and an initial pressure. To further boost biocrude yield, acetone was introduced as a co-solvent. Utilizing a solvent mixture with a higher proportion of acetone than water (on a volume basis) enhanced biocrude yield, reaching a maximum value of 83.9 wt%. Comprehensive characterization through Fourier transform infrared spectroscopy, ultimate analysis, a Van Krevelen diagrammatic assessment, and gas chromatography-mass spectrometry analyses revealed the underlying reaction mechanism of the co-HTL process, demonstrating that acetone reduces the polarity of the reaction medium, thereby shifting the partitioning of PLA-derived organic acids from the aqueous product into the biocrude. Consequently, the atomic O/C ratio decreased while the higher heating value (HHV) increased, indicating an improvement in biocrude quality. These observations highlight that the introduction of acetone as a co-solvent during the co-HTL of PLA and SCG is an effective strategy for simultaneously maximizing biocrude yield and improving its overall quality.

Mesoporous cerium dioxide (CeO₂) has attracted considerable attention for oxidation catalysis due to its reversible Ce⁴⁺/Ce³⁺ redox couple and oxygen storage capability. However, the catalytic performance of CeO₂ strongly depends on synthesis conditions that govern mesostructure development and defect formation. In this study, surfactant-templated mesoporous CeO₂ was synthesized using cetyltrimethylammonium bromide (CTAB) and Pluronic F127 as structure-directing agents. Response surface methodology (RSM) based on a Box–Behnken design was employed to systematically evaluate the effects of pH, metal-to-surfactant ratio, and hydrothermal temperature on textural properties and CO oxidation activity. Statistically validated models revealed distinct parameter sensitivities for CTAB- and F127-templated systems. Optimized catalysts exhibited significantly enhanced catalytic performance compared with suboptimal and commercial CeO₂, achieving markedly lower light-off temperatures. Structural characterization demonstrated that optimization promoted smaller crystallite size, well-developed mesoporosity, and increased Ce³⁺ fraction accompanied by enriched oxygen vacancies and surface-active oxygen species. H₂-TPR analysis further confirmed improved reducibility and enhanced oxygen mobility in optimized samples. The superior CO oxidation activity was attributed to defect-engineered surfaces facilitating oxygen activation via a Mars–van Krevelen mechanism. This work establishes a quantitative synthesis–structure–redox–activity relationship and demonstrates that statistical optimization combined with surfactant-templated design is an effective strategy for engineering high-performance mesoporous CeO₂ catalysts.

This study introduces a sustainable and environmentally friendly process for selective co-extraction of Ni²⁺ and Co²⁺ from leaching solution of spent ternary lithium-ion batteries (LIBs) with neodecanoic acid (V10). The extraction conditions were systematically optimized, and a process for reducing extractant dissolution loss in the raffinate was specifically designed, with both the extraction and extractant recovery steps integrated into a continuous mixer-settler operation. Experimental results showed that under optimal conditions, the extraction efficiency of Ni and Co consistently exceeded 99.9%, and the concentrations of Li and Mg in the strip solution remained below 1 mg/L. This process achieved both ultra-high extraction of Ni and Co and deep separation from Mg and Li. Furthermore, the chemical oxygen demand (COD) of the raffinate was reduced from around 10,000 mg/L to below 1,000 mg/L, demonstrating the effectiveness of this method in significantly decreasing COD. In addition, the extraction mechanism and the mechanism for reducing extractant dissolution loss were also verified. This work provides insights for developing a potentially practical process based on the V10 extraction system to improve selective co-extraction of Ni and Co from complex solutions while reducing extractant dissolution loss.

Electrochemical nitrogen reduction reaction (eN2RR) is a highly promising approach for ammonia synthesis under normal temperature and pressure conditions. However, its practical application is limited by the low activity and selectivity of the catalysts. In this study, a series of Fe-MOFs materials were prepared by hydrothermal method, and further sintered to obtain Fe@C materials. The electrocatalytic performance of these materials in eN2RR was systematically investigated. The results showed that MIL-53(Fe)-2 exhibited excellent catalytic activity at -0.4 V vs. RHE, with an ammonia production rate of 1.443 µg·h⁻¹·mg⁻¹ and a Faradaic efficiency of 5.972%. In contrast, the Fe@C material derived from MIL-53(Fe)-1, although having rapid activation characteristics within a narrow potential window, did not perform as well as the former. This work provides a new material strategy and experimental basis for the design of iron-based eN2RR catalysts.

Fossil fuels are carbon sources that account for a significant 80% of energy supply. Electricity-based fuel (e-fuel) and biofuel are attracting attention as technologies that produce alternative fuels to these fossil fuels. Among low-carbon eco-friendly materials, dimethyl ether (DME) is of high interest as it can be used as both e-fuel and biofuel. In this study, three raw materials, i.e. syngas, biogas, mix of captured CO₂ and green H₂, are used to compare DME fuel production process. Furthermore, by comparing two synthesis routes, techno-economic analysis and environmental impact evaluation are conducted for the six processes. As a result, the most eco-friendly process was the CO₂ and H₂-based indirect synthesis process with 0.24 ton-_CO2/ton-_DME, and the most cost-competitive process was the syngas-based direct synthesis process with 434 $/ton-_DME. Meanwhile, considering the minimum DME selling price (MDSP), only CO₂ and H₂-based DME processes (i.e., 1,938 $/ton-_DME and 2,633 $/ton-_DME for the indirect and direct route, respectively) are more expensive than fossil fuel. However, with advances in hydrogen technology and the implementation of carbon taxes, the MDSP decreases by about 48.7% and 50.4%, respectively, suggesting its potential as a cost-competitive alternative fuel.

Plant-based metal oxide nanoparticles have gained considerable interest in recent years due to their important biological applications. The present study aimed to synthesize, characterize, and test the environmental applications of a Manilkara zapota leaf-wrapped CaO–CuO nanocomposite. A phytochemical-rich extract was used as a reducing or stabilizing agent during synthesis; therefore, the synthesis route was entirely eco-friendly. The fabrication and structural properties were confirmed using UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Atomic force microscopy (AFM). XRD analysis confirmed the crystalline structure, and TEM revealed that the nanocomposite was nearly spherical, with an average size of 22.41 nm. Optical studies showed a direct band gap energy of 3.32 eV, providing evidence of the semiconductor behavior of the nanocomposite. The antioxidant and anti-inflammatory activities reached their maximum values at 250 µg/mL and 50 µg/mL, respectively, indicating progressive free radical scavenging and anti-inflammatory potential. The inhibition zone diameter was determined to be 13.51, 14.25, 14.31, and 16.8 mm for Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. P. aeruginosa exhibited maximum antimicrobial and antibiofilm activity at a nanocomposite concentration of 100 µg/mL. Furthermore, the photocatalytic activity of the nanocomposite was investigated, achieving 81.14% Congo red dye decolorization under 80 min of sunlight irradiation. The reaction was followed by the first-order kinetic model with a constant rate of 0.0219 min^− 1. This study demonstrates that the green-synthesized CaO–CuO nanocomposite holds significant promise as a sustainable, multi-target material for biomedical and environmental remediation applications.