Magnesium oxide (MgO) exhibits excellent synergy with cerium oxide (CeO2), serving as either textural or electronic promoters during catalytic reactions. However, achieving well-dispersed CeO2-MgO is technically challenging because they are known not to form solid solutions, and the crystal growth of CeO2 suppresses the structure formation of MgO, leading to MgO being in an inhomogeneous amorphous state within CeO2-MgO. For this reason, most of research groups have been struggling with synthesizing well-dispersed CeO2-MgO. This leads them to focusing on the interaction between the active metal and cerium, overlooking the true role of magnesium. In this study, we successfully synthesized well-dispersed CeO2-MgO via a spray pyrolysis-assisted evaporation-induced self-assembly method, followed by the impregnation of Cu. The location and dispersion of Cu nanoparticles were highly dependent on the MgO distribution. Additionally, we revealed that this significantly influenced the catalytic activity and stability towards the HTS reaction and furthermore supplies electrons to monovalent Cu species, helping maintain the stable electron structure and oxidation state of Cu species considered as active sites. These findings suggest that optimizing the MgO distribution in CeO2-MgO is a promising strategy for developing efficient catalysts for the HTS reaction, emphasizing the role of MgO in designing high-performance catalysts.

Direct ammonia solid oxide fuel cells (DA-SOFCs) offer a carbon-free power generation pathway by directly utilizing ammonia as a high-energy-density fuel with facile transportability. However, conventional Ni-based cermets, typically designed for hydrogen-fueled SOFCs, exhibit low catalytic activity for ammonia decomposition and are prone to metal nitride formation under DA-SOFCs operating conditions. Here, we present a novel strategy utilizing Ni nanoparticles-exsolved materials as a catalytic layer, which enhances the density of catalytically active sites, thereby facilitating the direct usage of ammonia in anode. No secondary phases were observed during high-temperature sintering with NiO and Sc-stabilized zirconia, indicating excellent chemical compatibility. Under operation conditions, the Ni nanoparticles are exsolved on the oxide surface, forming a highly dispersed socketing structure, which leads to high activity and durability. The Ni-exsolved catalysts display a higher density of active sites, thus exhibiting superior conversion activity compared to Ni-based composites with the same Ni content. The single cell incorporating the multi-functional catalyst layer exhibits a superior peak power density of 1.0 W/cm2 at 900 degrees C significantly higher than that of the reference cell without the layer (0.28 W/cm2). This study contributes to the advancement of multifunctional catalyst design and the direct conversion of non-hydrogen fuels without the need for external reforming in next-generation energy systems.

Reducing carbon dioxide emissions is one of the largest energy and environmental challenges currently faced globally. To achieve carbon neutrality, the development of new technologies and simultaneous improvement of conventional technologies are required. Catalysis, which determines the success or failure and efficiency of the process, is at the center of addressing these problems. Innovative advancements in catalysis have been accomplished through the extensive research on catalytic materials. Oxygen storage materials with oxygen storage capacity (OSC) have been widely applied in supports and active cocatalysts for energy and environmental catalytic applications. This review provides knowledge on the extended applications (reforming, water-gas shift reaction, and partial oxidation of methane (POM) for high-value-added chemicals, including hydrogen production, deoxygenation of fatty acids for second-generation biofuel production, selective catalytic reduction of NOx with NH3, hydrocarbon (HCs) oxidation for emission control, CO oxidation for vehicle exhaust control and purification of gaseous product fuel, and soot oxidation for the removal of motor-type pollutants) of these materials, which are mainly used as three-way catalysts (TWC) in automotive catalysis, to the carbon-neutral field. In particular, this study focuses on the physico-chemical properties that are closely synergistic with OSC, such as reducibility, dispersion, surface acid/base properties, and physical properties, such as surface structure or morphology.

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Charcoal canisters are widely used devices for measuring radon concentration in the atmosphere, but they are sensitive to humidity. A newly designed super absorbent polymer (SAP) filter was applied to charcoal canisters to enhance their resistance to ambient humidity, thereby improving the accuracy of radon concentration measurements. The charcoal canister with the SAP filter had an error of approximately 1.3-2.6% compared to the reference value (measured by RAD7), whereas the charcoal canister without the SAP filter exhibited an error of 12-18% compared to the reference value. Additionally, the charcoal canister with the SAP filter demonstrated over 90% of response value even under very high relative humidity conditions of 90%, indicating strong resistance to ambient humidity.

Biofuel is an eco-friendly fuel that can reduce CO2 emissions by 65% compared to using petroleum-based fuels. The commercialized biodiesel, which contains oxygen atom within its molecules, is only used in blends with petroleum-based diesel, but renewable diesel, diesel-like hydrocarbons, can completely substitute petroleum-based fuels. However, in the deoxygenation process to produce renewable diesel and jet fuel, solvents are injected to enhance the physical properties of reactants and the supply of hydrogen, thereby increasing the process expenditure. Therefore, in this review, the research results published over the past 10 years regarding the production of renewable fuels under solvent-free conditions have been critically reviewed. The effects of feedstocks, atmospheric conditions (type of gas and pressure), reaction temperature/time, catalyst type and its loading on the reaction mechanism and catalytic performance are carefully compared. Fatty acids and triglycerides require deoxygenation reactions, while furan compounds necessitate not only deoxygenation but also aldol condensation reactions to produce renewable biofuel. Higher H2 pressure and reaction temperature can enhance the reaction activity, but these parameters should be optimized while considering the process cost and side reactions. Noble metal catalysts have been reported to exhibit high deoxygenation activity, but for economic reasons, non-noble transition metals are being widely investigated. Ni is the most commonly used catalysts, and the deoxygenation mechanism varies depending on the acidity and type of acid sites on the catalyst. The feasibility of biofuels produced by solvent-free deoxygenation is assessed by comparing fuel properties with commercial diesel and jet fuel.

Herein, we verify pre-reduction conditions and H2O/CO ratio to increase activity in the HTS using Fe-Cr catalyst. It was determined that the optimal H2O/CO ratio was 2.5 through the result of calculated thermodynamic equilibrium analysis and performed HTS reaction. In the Fe-Cr catalyst, HTS reaction was performed at 350 similar to 550 degrees C to find the condition that Fe2O3 convert Fe3O4 without over-reduction after reduced using 2% H-2/N-2, 5% H-2/N-2, and reactant gas at various temperature (400, 500, and 600 degrees C). The lower the pre-reduction temperature, the higher CO conversion, but the effect of the pre-reduction gas was not significant. In addition, as a result of performing a stability test that reduced using reactant gas at 400, 500, and 600 degrees C, all of which maintained stability without deactivation even though had a large range of CO conversion for 50 h. Thus, we identify that the appropriate H2O/CO ratio for HTS reaction using gas produced from waste gasification is judged to be 2.5. And during the reaction using Fe-Cr, the CO conversion showed high activity when pre-reduction temperature is 400 degrees C. In the case of the pre-reduction gas, the activity was insignificantly affecting the pre-reduction at 400 degrees C, thus it is considered appropriate to use reactant gas for practical use without the need to connect the pre-reduction gas separately.

Herein, we investigated the main active sites and structure-sensitivity of the water-gas shift (WGS) reaction over ternary Cu–ZnO–Al2O3 (CZA) catalysts. CZA catalysts with various Cu contents were synthesized by the homogeneous one-step coprecipitation method. The Cu content mainly affected the number of active Cu sites and was closely related to the WGS activity. Turnover frequency (TOF) values were independent of Cu dispersion, indicating that the CZA catalyst is structure-insensitive in WGS. The ratio of surface Cu+ species also strongly influenced the activity of the CZA catalyst. TOF based on the total active Cu species showed a constant value, but the CO conversion was linearly increased with the number of surface Cu+ species.

Hydrogen, a clean energy carrier, can be produced from renewable sources such as biomass and waste, but it is needed to develop new catalysts with high resistance against impurities. Ni/Al2O3 yolk-shell catalysts were prepared by different procedure for the steam reforming of methane reaction with alkali poisoning. Yolk-shell (ys) and porous yolk-shell (pys) materials were synthesized using a spray pyrolysis process. The physicochemical and structural properties of the prepared catalysts on the reaction performance and alkali resistance were investigated. All the yolk-shell catalysts exhibited high resistance to carbon deposition. The Ni/pys-Al2O3 catalyst showed the highest CH4 conversion and the best stability at a gas hourly space velocity of 932,492 mL center dot g(-1)center dot h(-1) even upon exposure to alkali hydroxide vapor. It also showed strong resistance to sintering, whereas the structures of the ys-Ni-Al2O3 and Ni/ys-Al2O3 catalysts were relatively degraded under the same conditions.

In this study, we synthesized a Cu-ZrCeO2 catalyst with a yolk-shell structure, exhibiting high activity, stability, and reusability at high temperatures. It was applied to the high-temperature water-gas shift reaction under practical waste-derived synthesis gas conditions. Various reducible supports were utilized, including CeO2, ZrO2, TiO2, ZrCeO2, and TiCeO2. Among these, the Cu-ZrCeO2 catalyst (YCZC) displayed the highest activity and stability. Due to its high oxygen storage capacity and abundant defect oxygen, the YCZC catalyst demonstrated a CO conversion rate of 76% and 100% CO2 selectivity, even at a temperature of 400°C. Additionally, it maintained stable catalytic performance for 50 hours, attributed to its Cu sintering resistance and the retention of the yolk-shell structure, indicating its high reusability. A comprehensive deactivation study was conducted on deactivated catalysts. When using CeO2 as the sole support, rapid Cu sintering was observed, and the yolk-shell structure was not retained, leading to its collapse. Catalysts supported on ZrO2, TiO2, and TiCeO2 experienced Cu sintering and carbon deposition, leading to their deactivation.

Achieving Net Zero 2050 through decarbonization and securing next-generation clean energy have become the most important challenges. One of the pathways that make these possible is the paradigm shift to the hydrogen economy society. “Blue hydrogen” production controls CO2 emissions by applying carbon capture, utilization and storage (CCUS) technology to the existing gray hydrogen process. Performance improvement by identifying key performance-influencing factors of materials for each unit can be a valid approach to effectively solve the aforementioned issues. This review highlights the recent relevant research on materials applied to each unit process of blue hydrogen production (catalysts for reforming, water-gas shift, preferential oxidation, sorbents and oxygen carriers for desulfurization, pressure swing adsorption, CCUS) and deals with key performance-influencing factors and acceptable performance criteria for integration with CCUS. For desulfurization, PSA, and CCUS sorbents, maintaining pore structure is crucial. Performance can be improved by combining liquid and solid adsorbents, as well as using specific molecular sieves and porous supports. In reforming, water-gas shift, and preferential oxidation, achieving high metal dispersion is crucial. Enhancing metal-support interaction through proper support application prevents sintering and boosts catalytic performance.

The environmental impact of increasing waste emissions and the demand for clean energy have led to the development of waste-to-energy technologies. Hydrogen, a clean energy carrier, can be produced via the water gas shift (WGS) reaction, accompanied by waste gasification. CuFe2O4 spinel ferrite has been synthesized by various methods, such as co-precipitation, electrospinning, dehydration, sol-gel, and hydrothermal methods, and has been applied to the WGS reaction of waste-derived syngas. Among the different methods, the electrospinning method affords nanofiber-structured CuFe2O4, which showed the highest WGS activity which is attributed to its remarkable reducibility and easier formation of active species. It was also found that the distinct nanofiber structure of this catalyst prevents Cu sintering at high temperatures, resulting in stable activity during the WGS reaction.

Hydrogen is mainly produced by steam reforming of fossil fuels. Thus, research has been continuously conducted to produce hydrogen by replacing fossil fuels. Among various alternative resources, waste is attracting attention as it can produce hydrogen while reducing the amount of landfill and incineration. In order to produce hydrogen from waste, the water–gas shift reaction is one of the essential processes. However, syngas obtained by gasifying waste has a higher CO concentration than syngas produced by steam reforming of fossil fuels, and therefore, it is essential to develop a suitable catalyst. Research on developing a catalyst for producing hydrogen from waste has been conducted for the past decade. This study introduces various catalysts developed and provides basic knowledge necessary for the rational design of catalysts for producing hydrogen from waste-derived syngas.

CeO2 supports have been synthesized through a different precipitation/digestion method with various cerium precursors (cerium hydroxide (CH), cerium hydroxy carbonate (CHC), cerium carbonate (CC)). Nano-sized CeO2 supports with a high BET surface area were prepared through the pre-calcination of cerium precursors. 20 wt.% of Cu was loaded onto the prepared CeO2 supports through an incipient wetness impregnation method. Among the prepared catalysts, Cu/CeO2-CHC yielded the highest CO conversion between the temperature range from 200 to 360 degrees C. This result was primarily due to possessing the highest Cu dispersion and a high oxygen storage capacity (OSC). In addition, the 20 wt.% Cu/CeO2 catalyst exhibited 100 % CO2 selectivity.

Ni/MgO-Al2O3 (Ni/MG70) catalysts were developed for the deoxygenation reaction to produce green diesel from non-edible fatty acids. As the Ni loading amount was increased from 5% to 30%, the characteristics of the catalysts, such as Brunauer-Emmett-Teller (BET) surface area, Ni dispersion, reducibility, number of Ni active sites, and acidity, varied. Among the prepared catalysts, the 20% Ni/MG70 catalyst showed excellent deoxy-genation performance owing to its highest number of Ni active sites, easier reducibility, and appropriate acidity. Furthermore, it was confirmed that deoxygenation in this study was carried out via the hydrodeoxygenation reaction pathway to remove oxygen species as H2O. In addition, the basic fuel properties, calorific value and viscosity, were analyzed for produced green diesel.

The Ni-MgO (NM) and Ni-MgO-CeO2 (NMC) catalysts prepared by co-precipitation at different titration rates have been applied to carbon dioxide reforming of methane (CDR). The effects of titration rates on the catalytic properties and reaction behaviors of the catalyst were varied significantly depending on the CeO2 addition. The titration rate mainly influenced the physical properties, such as Ni crystallite size and Ni dispersion, in NM catalysts, but for the NMC catalysts, chemical properties, such as oxygen storage capacity, also were affected. Regarding the change of titration rates, the NM catalysts exhibited the difference of activity, but NMC catalysts showed the difference of activity as well as stability. As a result, the NMC catalyst prepared at fast titration rate achieved the highest catalytic CDR performance at 800 degrees C and a high gas hourly space velocity of 720,000 mL.g(-1).L-1.