Search Results (771)

Trace amounts of CO in H₂-rich gas can poison Pt electrodes in proton-exchange-membrane fuel cells, necessitating selective CO removal. Preferential oxidation of CO (PROX) offers an efficient route to oxidize CO while preserving H₂. Although noble-metal-based catalysts are widely used, their high cost has driven interest in non-precious alternatives. Co₃O₄–CeO₂ catalysts have emerged as particularly promising due to their high activity and stability. Two series of Co–Ce/SiO₂ catalysts were prepared via impregnation: in the first, Ce was introduced and calcined prior to Co deposition; in the second, Co and Ce nitrates were co-deposited from a mixed aqueous solution. The latter method enhances the interaction between Co₃O₄ and CeO₂, increasing the availability of surface oxygen species. Stability tests on the most active sample demonstrated remarkable durability, maintaining near-complete CO conversion over 100 h on dry stream. Full article

MXenes, a family of two-dimensional transition metal carbides and nitrides, exhibit exceptional electrical conductivity, tunable surface chemistry, and strong broadband light absorption. However, their practical implementation is often limited by structural instability, such as restacking and surface oxidation. In this study, we propose a strategy for the design of hybrid nanocomposites based on exfoliated Ti₃C₂T_x MXene embedded within a porous silica (SiO₂) matrix and further functionalized with cerium dioxide (CeO₂) nanoparticles. The SiO₂ matrix, synthesized via a sol–gel approach, ensures homogeneous dispersion, increased porosity, and thermal stability, effectively reducing MXene restacking. Simultaneously, CeO₂ nanoparticles create surface oxygen vacancies and enhance interfacial reactivity. Comprehensive structural, morphological, surface, and optical characterizations confirm the formation of stable, light-responsive nanoarchitectures with tailored textural properties. Furthermore, the obtained material exhibit promising photothermal-catalytic properties. This work offers a materials-oriented approach for engineering multifunctional MXene-based architectures with enhanced photothermal performance, exemplified by their potential application in the photothermo-catalytic CO₂ conversion into solar fuels, showcasing the broader possibilities enabled by these materials. Full article

A targeted modification approach involving the synthesis of Ce/C co-doped TiO₂ aerogels (CeCTi) via a sol–gel method combined with supercritical CO₂ drying and subsequent heat treatment is employed to enhance the photocatalytic CO₂ reduction performance of cost-effective and stable TiO₂ aerogels. The results demonstrate that the CeCTi exhibits a pearl-like porous network structure, an optical band gap of 2.90 eV, and a maximum specific surface area of 188.81 m²/g. The black aerogel sample shows an enhanced light absorption capability resulting from the Ce/C co-doping, which is attributed to the formation of oxygen vacancies. Under simulated sunlight irradiation, the production rates of CH₄ and CO reach 27.06 and 97.11 μmol g⁻¹ h⁻¹ without any co-catalysts or sacrificial agents, respectively, which are 82.0 and 5.7 times higher than those of the pristine TiO₂ aerogel. DFT reveals that C-doping facilitates the formation of oxygen vacancies, which introduces defect states within the calculational band gap of TiO₂. The proposed photocatalytic mechanism involves the light-induced excitation of electrons from the valence band to the conduction band, their trapping by oxygen vacancies to prolong the charge carrier lifetime, and their subsequent transfer to adsorbed CO₂ molecules, thereby enabling efficient CO₂ reduction, which is experimentally supported by photoluminescence measurements. Full article

The horst and graben system in Western Anatolia lies on the eastern boundary of the Aegean extensional system, one of the most active extensional zones in the world. The Şahinali coal basin is located south of the Büyük Menderes Graben, which is part of this system. This study examines the rare earth elements and yttrium (REY) geochemistry, accumulation conditions, and economic potential of the Şahinali coals. Compared to world coals, the REE concentration in Şahinali coals (208.3 ppm) is quite high, and all REY groups are slightly enriched. Light REY (LREY) is dominant compared to medium REY (MREY) and heavy REY (HREY). The most abundant element in this group is Ce, reaching a concentration of 123.3 ppm. REY distribution patterns indicate H-type enrichment in most samples and, to a lesser extent, M-H-type enrichment. Element ratios (Al₂O₃/TiO₂, TiO₂/Zr, La/Sc, Co/Th) and REY anomalies (Ce, Eu, Gd) indicate that the sedimentary input is predominantly derived from felsic rocks, with limited intermediate to mafic contributions. SEM-EDS findings and correlation analyses indicate that REY are predominantly associated with aluminosilicate minerals. LREY-Th and MREY/HREY-Y relationships are supported by monazite and Y-rich illitic K-aluminosilicates. Paleoenvironmental indicators (V/Cr, Ni/Co, U/Th, Sr/Cu, Rb/Sr, Sr/Ba) indicate that the coal accumulated under oxic–suboxic, warm and humid conditions. The average REY oxide (REO) content slightly exceeds the commonly cited 1000 ppm screening threshold for coal ash. The majority of samples contain elevated proportions of critical REY (30.7%–54.3%) and show promising outlook coefficients (C_outl: 0.8–1.7). Together, these results indicate a favourable compositional signature for preliminary REY resource screening in the Şahinali coals, particularly with respect to elements relevant for high-technology applications. Full article

Little is known of a large black shale belt within the Naij Tal Group in the East Kunlun region, which hosts polymetallic deposits, including manganese, vanadium, and cobalt. The recently discovered Dagangou vanadium mineralization is the first black rock series-type vanadium deposit in the East Kunlun region and Qinghai Province and represents a significant find owing to its intermediate scale. This study investigated the mineralogy, major and trace elements, rare earth elements, and platinum group element geochemistry of the Dagangou vanadium deposit. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that the main vanadium-bearing minerals are micas, followed by limonite, clay minerals, feldspar, and jarosite. The SiO₂/Al₂O₃, Co/Zn, Sr/Ba, and Pd/Ir ratios, as well as the Ir content of the ores, indicated strong involvement of hydrothermal activity in the mineralization process. The V/Cr, Ni/Co, and U/Th ratios, as well as the δU values and significant negative δCe anomalies, suggested that the vanadium-bearing black rock series formed in a strongly anoxic reducing environment. The Al₂O₃/(Al₂O₃ + Fe₂O₃) and MnO/TiO₂ ratios, along with weak positive δEu anomalies and strong enrichment of heavy rare earth elements, indicated that mineralization occurred in an extensional tectonic setting. The black shale-hosted vanadium polymetallic deposit formed in a setting that transitioned from an open oceanic deep-sea environment to a progressively shallower continental margin. Full article

Partial oxidation of methane is a highly attractive route for hydrogen-rich syngas production, provided that high H₂ yields and H₂/CO ratios above 3 can be achieved. Herein, we demonstrate that precise compositional tuning of Ni–Cu bimetallic catalysts supported on Gd-doped CeO₂ enables direct control over defect chemistry and reaction pathways in partial oxidation of methane. A systematic investigation of Ni/Cu ratios was conducted to elucidate composition–structure–activity relationships using X-ray diffraction, Raman spectroscopy, temperature-programmed reduction/oxidation/desorption, and thermogravimetric analysis. While monometallic 5%Ni/GDC and promoted 1%Re4%Ni/GDC exhibited high methane conversion, they failed to deliver optimal hydrogen selectivity. In contrast, introducing Cu within a narrow compositional window fundamentally altered the reaction mechanism. The 2.5%Ni2.5%Cu/GDC catalyst showed limited oxygen vacancy formation and pronounced carbon deposition, leading to inferior catalytic performance. Remarkably, the 3.5%Ni1.5%Cu/GDC catalyst maximized both oxygen vacancy density and surface basicity, thereby selectively activating CO₂- and H₂O-assisted oxidation routes and enforcing the exclusive dominance of indirect POM pathways. This defect-mediated pathway control effectively decoupled methane activation from hydrogen-consuming side reactions while simultaneously promoting hydrogen-forming, CO-consuming reactions, most notably the water–gas shift reaction. As a result, the optimized 3.5%Ni1.5%Cu/GDC catalyst achieved an H₂ yield of 84% with an H₂/CO ratio of 3.11 and maintained stable operation for 40 h on stream at 600 °C. These findings establish Ni–Cu compositional tuning as a powerful strategy for defect engineering and reaction pathway regulation, providing new design principles for efficient and durable partial oxidation of methane catalysts targeting hydrogen-rich syngas production. Full article

The conventional treatment of high-concentration volatile organic compounds (VOCs) relies on energy-intensive dilution to avoid explosion risks. This study proposes an efficient catalytic combustion process treating VOCs directly within the explosive range while recovering reaction heat using Pt/γ-Al₂O₃-based catalysts promoted with La and Ce. Catalysts (0.05–0.5 wt% Pt) were synthesized via impregnation and characterized using FE-SEM, BET, and XRD. Catalytic combustion experiments at VOC concentrations up to 13,000 ppm showed combustion initiation below 200 °C, achieving 83–99% conversions at 300 °C with complete oxidation to CO₂. Although 5 vol.% moisture significantly inhibited low-temperature activity through competitive adsorption, La and Ce promoters (10 wt%) effectively overcame this limitation by increasing surface area (up to 194.93 m²/g) and oxygen mobility. The Ce-promoted catalyst demonstrated superior water tolerance, achieving complete conversion at 200–210 °C due to its high Oxygen Storage Capacity (OSC). Bench-scale validation using a 1 Nm³/h system confirmed industrial feasibility. Operating at 220 °C with 13,000 ppm toluene for 100 h, the catalyst maintained >99.98% conversion with negligible deactivation and THC emissions below 2 ppm. The double-jacket heat exchanger effectively managed reaction heat (limiting temperature rise to ~20 °C) and recovered it as steam. Compared to Regenerative Thermal Oxidation, this Regenerative Catalytic Oxidation approach reduced emissions and energy consumption. This work demonstrates a robust “combustion-with-recovery” strategy for high-concentration VOC treatment, offering a sustainable alternative with high efficiency, stability, and safe energy-integrated operation. Full article

Low-temperature CO oxidation is crucial for applications like gas purification and exhaust treatment, with ceria-based catalysts being highly promising. However, conventional synthesis methods often require energy-intensive calcination, releasing harmful gaseous contaminants. To address this, we demonstrate a facile and environmentally friendly method for preparing Ga₂O₃/CeO₂ catalysts by substituting gallium salt solution with liquid gallium, followed by room-temperature ball milling (BM). The resulting 1.5% Ga₂O₃-CeO₂ catalyst, milled at 300 rpm for 60 min, exhibited catalytic activity starting at 100 °C and achieved complete CO conversion at 300 °C. This work presents an economical and sustainable strategy that utilizes liquid metals to prepare high-performance ceria-based catalysts, offering a green alternative to traditional synthesis routes that rely on metal salts and high-temperature treatments. Full article

Advanced ceramics are known for their lightweight, high-temperature resistance, corrosion resistance, and biocompatibility. They are crucial in energy conversion, environmental protection, and aerospace fields. This review highlights the recent advancements in ceramic matrix composites, high-entropy ceramics, and polymer-derived ceramics, alongside various fabrication techniques such as three-dimensional printing, advanced sintering, and electric-field-assisted joining. Beyond the fabrication process, we emphasize how different processing methods impact microstructure, transport properties, and performance metrics relevant to catalysis. Additive manufacturing routes, such as direct ink writing, digital light processing, and binder jetting, are discussed and normalized based on factors such as relative density, grain size, pore architecture, and shrinkage. Cold and flash sintering methods are also examined, focusing on grain-boundary chemistry, dopant compatibility, and scalability for catalyst supports. Additionally, polymer-derived ceramics (SiOC, SiCN, SiBCN) are reviewed in terms of their catalytic performance in hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and CO₂ reduction reaction. CeO₂-ZrO₂ composites are particularly highlighted for their use in environmental catalysis and high-temperature gas sensing. Furthermore, insights on the future industrialization, cross-disciplinary integration, and performance improvements in catalytic applications are provided. Full article

This study investigates the oxidative steam reforming (OSR) of simulated bio-oil aqueous fractions using Co/CeO₂-SBA-15 catalysts. Five representative compounds—methanol, acetic acid, hydroxyacetone, phenol, and furfural—were evaluated to assess their reactivity for hydrogen production. Aliphatic compounds achieved nearly complete conversion and stable hydrogen yields, while aromatic structures led to lower conversion and higher coke formation. Furfural exhibited higher reactivity than phenol due to its furan ring and aldehyde group. Catalysts with 10 and 20 wt.% Ce showed similar activity, but Co/20CeO₂-SBA-15 presented lower hydrogen yield. For this reason, next experiments of OSR of model compound mixtures were carried out only with Co/10CeO₂-SBA-15. To approach real bio-oil complexity, ternary and quinary mixtures were tested. High conversion and hydrogen yield were maintained over 50 h when the ternary mixture (methanol, hydroxyacetone, and acetic acid) was fed. When the quinary mixture was used as feedstock, which includes furfural and phenol, lower conversions were obtained for these compounds compared to aliphatic ones, although conversions remained above 80% after 50 h (88.9% for furfural and 82.6% for phenol). These results highlight Co/10CeO₂-SBA-15 as a viable catalyst for bio-oil aqueous fraction valorization under OSR conditions. Full article

The reverse water–gas shift (RWGS) reaction serves as a highly flexible and critical pathway for converting CO₂ into CO, with Pt-based catalysts having been widely investigated. Here, a series of platinum-rare earth (RE) subnanometric bimetallic clusters (SBCs) were successfully prepared on carbon support by the potassium vapor reduction method. Their structure and electronic properties, along with catalytic performance, were systematically characterized and evaluated. The Pt-RE SBC catalysts exhibited excellent catalytic activity, maintaining CO selectivity above 95% at high CO₂ conversion levels and demonstrating stable operation over 100 h at 600 °C. Furthermore, the influence of different supports (carbon black and CeO₂) on the catalytic performance was compared. It was found that Pt-Sc SBCs supported on the carbon exhibited better dispersion, smaller particle size, and superior catalytic performance relative to the CeO₂ supported counterpart. This study provides new insights into the design of highly efficient and stable RWGS catalysts, highlighting the key role of the Pt-RE SBC interface synergistic effect and support selection, which is of great significance for the resource utilization of CO₂. Full article

The biogas dry reforming reaction offers a promising route for syngas production while simultaneously mitigating greenhouse gas emissions. Membrane reactors have proven to be an excellent option for hydrogen production and separation in a single unit, where conversion and yield can be enhanced over conventional processes. In this study, a Pd/YSZ membrane integrated with a Ru/CeO₂ catalyst was evaluated for biogas reaction under varying operating conditions. The selective removal of hydrogen through the palladium membrane improved reactant conversion and suppressed side reactions such as methanation and the reverse water–gas shift. Experiments were performed at temperatures ranging from 500 to 600 °C, pressures of 1–6 bar, and a gas hourly space velocity (GHSV) of 800 h⁻¹. Maximum conversions of CH₄ (43%) and CO₂ (46.7%) were achieved at 600 °C and 2 bar, while the maximum hydrogen recovery of 78% was reached at 6 bar. The membrane reactor outperformed a conventional reactor, offering up to 10% higher CH₄ conversion and improved hydrogen production and yield. Also, a comparative analysis between Ru/CeO₂ and Ni/Al₂O₃ catalysts revealed that while the Ni-based catalyst provided higher CH₄ conversion, it also promoted methane decomposition reaction and coke formation. In contrast, the Ru/CeO₂ catalyst exhibited excellent resistance to coke formation, attributable to ceria’s redox properties and oxygen storage capacity. The combined system of Ru/CeO₂ catalyst and Pd/YSZ membrane offers an effective and sustainable approach for hydrogen-rich syngas production from biogas, with improved performance and long-term stability. Full article

The conversion of CO₂ into value-added chemicals exemplifies an innovative and eco-friendly approach to addressing carbon emissions. In this study, shape-specific CeO₂ nanocrystals (nanorods, nanocubes, and nanoparticles) were successfully synthesized and employed as catalysts to study the structure-dependent behavior and reaction mechanism for one-step CO₂ conversion to diethyl carbonate (DEC). Among the three catalysts, CeO₂ nanorods (Ce-NR) exhibited the best catalytic activity in the synthesis of DEC from CO₂ compared with CeO₂ nanocubes (Ce-NC) and nanoparticles (Ce-NP), which achieved the DEC production of 1.32 mmol_DEC/g_cat at 423 K and 5 MPa for 4 h. Comprehensive characterization further confirmed the enhanced activity of Ce-NR originated from the morphology effect, particularly the promotion of oxygen vacancies and Ce³⁺ species, which promoted reaction activity. Furthermore, the Ce-NR catalyst almost retained 1.32 mmol_DEC/g_cat DEC production of its initial activity after four cycles, underscoring its exceptional stability and promising industrial scalability. These findings provide fundamental insights to guide the rational design of efficient catalysts for CO₂ activation and other critical transformations. Full article

A series of novel Ce-modified MnCoAl layered double oxides (Ce/MCA LDOs) were prepared using solvothermal and impregnation methods for NH₃-SCR denitration. Various characterizations, such as X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and H₂ temperature-programmed reduction (H₂-TPR) were used to investigate their structural properties and the mechanism of ammonia selective catalytic reduction (NH₃-SCR). The incorporation of Ce was found to effectively integrate into the LDO framework and enhance the catalytic activity over a wide temperature window. Moreover, the thermal stability and resistance of H₂O and SO₂ were evaluated. In situ DRIFTS studies revealed that the reaction follows both the “Langmuir–Hinshelwood” (L–H) and “Eley–Rideal” (E–R) mechanisms. This work provides systematic insights into the design of LDO-based catalysts, demonstrating their potential for practical application in denitration. Full article

The continuous tightening of emission regulations and the escalating costs of palladium (Pd) and rhodium (Rh) have renewed interest in platinum (Pt)-based three-way catalysts (TWCs) as cost-effective alternatives for gasoline aftertreatment. However, despite extensive studies on Pt/CeO₂ and Pt/Ba-based formulations, the cooperative roles of Ba and Ce and, in particular, the fundamental influence of the Ba/Ce ratio on oxygen mobility, NO_x storage behavior, and Pt–support interactions remain poorly understood. In this work, we address this gap by systematically tuning the Ba/Ce molar ratio in a series of Pt–Ba–Ce/Al₂O₃ catalysts prepared from Ba(CH₃COO)₂ and CeO₂ precursors, and evaluating their structure–function relationships in both fresh and hydrothermally aged states. Through comprehensive characterization (N₂ physisorption, XRD, XPS, H₂-TPR, NO_x-TPD, SEM, CO pulse adsorption, and dynamic light-off testing), we establish previously unrecognized correlations between Ba/Ce ratio–dependent structural evolution and TWC performance. The results reveal that the Ba/Ce ratio exerts a decisive control over catalyst textural properties, Pt dispersion, and interfacial Pt–CeO₂ oxygen species. Low Ba/Ce ratios uniquely promote Pt–Ce interfacial oxygen and O₂ spillover—providing a new mechanistic basis for enhanced low-temperature oxidation and reduction reactions—while higher Ba loading selectively drives BaCO₃ formation and boosts NO_x storage capacity. A clear volcano-type dependence of NO_x storage on the Ba/Ce ratio is demonstrated for the first time. Hydrothermal aging at 850 °C induces PtO_x decomposition, BaCO₃–Al₂O₃ solid-state reactions forming inactive BaAl₂O₄, and Pt sintering, collectively suppressing Pt–Ce interactions and reducing TWC activity. Importantly, an optimized Ba/Ce ratio is shown to mitigate these degradation pathways, offering a new design principle for thermally durable Pt-based TWCs. Overall, this study provides new mechanistic insight into Ba–Ce cooperative effects, establishes the Ba/Ce ratio as a critical and previously overlooked parameter governing Pt–support interactions and NO_x storage, and presents a rational strategy for designing cost-effective, hydrothermally robust Pt-based alternatives to Pd/Rh commercial TWCs. Full article