Search Results (36)

Mono- and di-substituted cerium oxide catalysts, viz. Ce_0.95Cu_0.05O_2-δ, Ce_0.90Cu_0.10O_2-δ, Ce_0.90 Cu_0.05Mn_0.05O_2-δ, Ce_0.85Cu_0.10Mn_0.05O_2-δ, and Ce_0.80Cu_0.10Mn_0.10O_2-δ, were synthesized via a one-step urea-assisted solution combustion method. The elemental composition and textural and structural properties of the catalysts were determined by various physical, electronic, and chemical characterization techniques. Hydrogen temperature-programmed reduction showed that co-doping of copper and manganese ions into the CeO_2-δ lattice improved the reducibility of copper. Powder XRD, XPS, HR-TEM, and Raman spectroscopy showed that the catalysts were a singled-phased, solid-solution metal oxide with a cerium oxide cubic fluorite (cerianite) structure, and evidence of oxygen vacancies was observed. Catalytic results in the preferential oxidation of CO in a hydrogen-rich stream showed that complete CO conversion occurred between 150 and 180 °C. Furthermore, at 150 °C, Ce_0.90Cu_0.05Mn_0.05O_2-δ, Ce_0.90 Cu_0.10O_2-δ, and Ce_0.85Cu_0.10Mn_0.05O_2-δ catalysts were the most active, achieving complete CO conversion and CO₂ selectivity of 81, 79, and 71%, respectively. The catalysts performed moderately in the presence of CO₂ and water, with the Ce_0.90Cu_0.05Mn_0.05O_2-δ catalyst giving a CO conversion of 80% in CO₂, which decreased to about 60% when water was added. Full article

Preferential oxidation of carbon monoxide (CO-PROX) in H₂-rich mixture is an effective way of hydrogen purification for fuel cells. High-performance PtCo/ZSM-5 catalysts with reduced Pt loading for this process were prepared using polynuclear platinum acetate complex known as platinum acetate blue (PAB) of the empirical formula Pt(CH₃COO)_2.5 as a novel precursor. The impregnation of HZSM-5 (Si/Al = 15 and 28) with PAB and its decomposition at 200 °C resulted in the stabilization of highly dispersed Pt⁰ and PtO_x species on the zeolite surface. The catalytic properties were improved by the addition of Co(CH₃COO)₂ followed by calcination at 450 °C. Produced materials were studied by SEM, TEM, EDX, XPS, and DRIFTS methods and tested in a CO-PROX reaction. The relationship between the synthesis conditions, structure, and catalytic behavior of composites is discussed in this paper. The synergistic effect of Pt and Co was observed when they both were located together in zeolite channels. The Pt-Co interaction provides new active catalytic sites and prevents platinum aggregation during the process. Due to this, the 100% CO conversion in the wide temperature range from 50 to 130 °C is achieved for PtCo/ZSM-5 catalysts (Si/Al = 15), which is the best result compared to low-loaded Pt catalysts prepared with traditional precursors. Full article

Preferential oxidation of CO (CO-PROX) has tremendous significance in purifying hydrogen for fuel cells to avoid catalyst poisoning by CO molecules. Traditional powder catalysts face numerous challenges, including high pressure drop, aggregation tendency, hotspot formation, poor mass and heat transfer efficiency, and inadequate thermal stability. Accordingly, ceramic monolithic catalysts, known as their excellent thermal stability, high surface area, and superior mass and heat transfer characteristics, are gaining increasing research attention. This review examines recent studies on ceramic monolithic catalysts in CO-PROX, placing emphasis on the regulation of active sites (e.g., precious metals like Pt and Au, and non-precious metals like CuO and CeO₂), monolith structures, and coating strategies. In addition, the structure–catalytic performance relationships, as well as the potential and limitations of different ceramic monolithic catalysts in practical application, are discussed. Finally, the challenges of monolithic catalysts and future research prospects in CO-PROX reactions are highlighted. Full article

An effect of Cu powder dispersion and morphology on the surface structure and the physical–chemical and catalytic properties of Cu–CeO₂ catalysts prepared by mechanochemical synthesis was studied in the preferential CO oxidation in a H₂-rich stream (CO-PROX). Two catalysts, produced by 30 min ball-milling from CeO₂ and 8 mass% of copper powders and with particle sizes of several tens (dendrite-like Cu) and 50–200 nm (spherical Cu obtained with levitation-jet method), respectively, were characterized by X-ray diffraction and electron microscopy methods, a temperature-programmed reduction with CO and H₂, and with Fourier-transform infrared spectroscopy. The catalyst synthesized from the “large-scale” dendrite-like Cu powder, whose surface consisted of Cu_xO (Cu⁺) agglomerates located directly on the surface of facetted CeO₂ crystals with a CeO₂(111) and CeO₂(100) crystal planes exposition, was approximately two times less active at 120–160 °C than the catalyst synthesized from the fine Cu powder, whose surface consisted of Cu_xO (Cu²⁺) clusters of 4–6 nm in size located on the steps of facetted CeO₂ nanocrystals. Although a large part of CO₂ reacted with a ceria surface to give carbonate-like species, no blockage of CO-activating centers was observed due to the surface architecture. The surface structure formed by the use of highly dispersed Cu powder is found to be a key factor responsible for the catalytic activity. Full article

Hydrogen for building fuel cells is primarily produced by natural-gas steam-reforming reactions. Pipeline-transported natural gas in Europe and North America used to contain about 1% to 5% N₂, which reacts with H₂ in steam-reforming reactions to form NH₃. In the case of Ru, one of the catalysts used in natural-gas steam-reforming reactions, the activity of the NH₃-formation reaction is higher than that of Ni and Rh catalysts. Reforming gas containing NH₃ is known to poison Pt catalysts in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and also poison catalysts in preferential oxidation (PROX). In this study, Langmuir–Hinshelwood-based models of the NH₃-formation reaction considering H₂ and CO were proposed and compared with a simplified form of the Temkin–Pyzhev model for NH₃-formation rate. The kinetic parameters of each model were optimized by performing multi-objective function optimization on the experimental results using a tube-type reactor and the numerical results of a plug-flow one-dimension simple SR (steam-reforming) reactor. Full article

Background: Age-related macular degeneration (AMD) is a progressive ocular ailment causing age-associated vision deterioration, characterized by dysregulated immune cell activity. Notably, follicular helper T (Tfh) cells have emerged as pivotal contributors to AMD pathogenesis. Nonetheless, investigations into Tfh-associated gene biomarkers for this disorder remain limited. Methods: Utilizing gene expression data pertinent to AMD procured from the Gene Expression Omnibus (GEO) repository, we employed the “DESeq2” R software package to standardize and preprocess expression levels. Concurrently, CIBERSORT analysis was utilized to compute the infiltration proportions of 22 distinct immune cell types. Subsequent to weighted gene correlation network analysis (WGCNA), coupled with differential expression scrutiny, we pinpointed genes intricately linked with Tfh cells. These potential genes underwent further screening using the MCODE function within Cytoscape software. Ultimately, a judicious selection of pivotal genes from these identified clusters was executed through the LASSO algorithm. Subsequently, a diagnostic nomogram was devised based on these selected genes. Results: Evident Tfh cell disparities between AMD and control cohorts were observed. Our amalgamated analysis, amalgamating differential expression data with co-expression patterns, unveiled six genes closely associated with Tfh cells in AMD. Subsequent employment of the LASSO algo-rithm facilitated identification of the most pertinent genes conducive to predictive modeling. From these, GABRB3, MFF, and PROX1 were elected as prospective diagnostic biomarkers for AMD. Conclusions: This investigation discerned three novel biomarker genes, linked to inflammatory mechanisms and pivotal in diagnosing AMD. Further exploration of these genes holds potential to foster novel therapeutic modalities and augment comprehension of AMD’s disease trajectory. Full article

HIV-associated epidemic Kaposi sarcoma (EpKS) remains one of the most prevalent cancers in sub-Saharan Africa despite the widespread uptake of anti-retroviral therapy and HIV-1 suppression. In an effort to define potential therapeutic targets against KS tumors, we analyzed previously published KS bulk tumor transcriptomics to identify cell surface biomarkers. In addition to upregulated gene expression (>6-fold) in the EpKS tumor microenvironment, biomarkers were selected for correlation with KSHV latency-associated nuclear antigen (LANA) expression. The cell surface glycoprotein genes identified were KDR, FLT4, ADAM12, UNC5A, ZP2, and OX40, as well as the endothelial lineage determinants Prox-1 and CD34. Each protein was evaluated for its expression and co-localization with KSHV LANA using multi-color immunofluorescence in KS tissues, KSHV-infected L1T2 cells, uninfected TIVE cells, and murine L1T2 tumor xenografts. Five surface glycoproteins (KDR, FLT4, UNC5A, ADAM12, and CD34) were associated with LANA-positive cells but were also detected in uninfected cells in the KS microenvironment. In vitro L1T2 cultures showed evidence of only FLT4, KDR, and UNC5A, whereas mouse L1T2 xenografts recapitulated human KS cell surface expression profiles, with the exception of CD34 and Prox-1. In KS tumors, most LANA-positive cells co-expressed markers of vascular as well as lymphatic endothelial lineages, suggesting KS-associated dedifferentiation to a more mesenchymal/progenitor phenotype. Full article

Background and Objectives: Impaired wound healing represents an unsolved medical issue with a high impact on patients’ quality of life and global health care. Even though hypoxia is a significant limiting factor for wound healing, it reveals stimulating effects in gene and protein expression at cellular levels. In particular, hypoxically treated human adipose tissue-derived stem cells (ASCs) have previously been used to stimulate tissue regeneration. Therefore, we hypothesized that they could promote lymphangiogenesis or angiogenesis. Materials and Methods: Dermal regeneration matrices were seeded with human umbilical vein endothelial cells (HUVECs) or human dermal lymphatic endothelial cells (LECs) that were merged with ASCs. Cultures were maintained for 24 h and 7 days under normoxic or hypoxic conditions. Finally, gene and protein expression were measured regarding subtypes of VEGF, corresponding receptors, and intracellular signaling pathways, especially hypoxia-inducible factor-mediated pathways using multiplex-RT-qPCR and ELISA assays. Results: All cell types reacted to hypoxia with an alteration of gene expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 1 (VEGFR1/FLT1), vascular endothelial growth factor receptor 2 (VEGFR2/KDR), vascular endothelial growth factor receptor 3 (VEGFR3/FLT4), and prospero homeobox 1 (PROX1) were overexpressed significantly depending on upregulation of hypoxia-inducible factor 1 alpha (HIF-1a). Moreover, co-cultures with ASCs showed a more intense change in gene and protein expression profiles and gained enhanced angiogenic and lymphangiogenic potential. In particular, long-term hypoxia led to continuous stimulation of HUVECs by ASCs. Conclusions: Our findings demonstrated the benefit of hypoxic conditioned ASCs in dermal regeneration concerning angiogenesis and lymphangiogenesis. Even a short hypoxic treatment of 24 h led to the stimulation of LECs and HUVECs in an ASC-co-culture. Long-term hypoxia showed a continuous influence on gene expressions. Therefore, this work emphasizes the supporting effects of hypoxia-conditioned-ASC-loaded collagen scaffolds on wound healing in dermal regeneration. Full article

New Pt-Co catalysts of hydrogen purification from CO impurities for fuel cells were fabricated via the deposition of monodispersed 1.7 nm Pt nanoparticles using laser electrodispersion on Co-modified ZSM-5 prepared by the Co(CH₃COO)₂ impregnation. The structure of prepared Pt-Co zeolites was studied by low-temperature N₂ sorption, TEM, EDX, and XPS methods. The comparative analysis of samples with different Pt (0.01–0.05 wt.%) and Co (2.5–4.5 wt.%) contents on zeolites with the ratio of Si/Al = 15, 28, and 40 was performed in the CO-PROX reaction in H₂-rich mixture (1%CO + 1%O₂ + 49%H₂ + 49%He). The synergistic catalytic action of Pt and Co on zeolite surface makes it possible to completely remove CO from a mixture with hydrogen in a wide temperature range from 50 to 150 °C; the high efficiency of designed composites with low Pt loading is maintained for a long time. The enhancement of PROX performance originates from the formation of new active sites for the CO oxidation at the Pt-Co interfaces within zeolite channels and at the surface. In terms of their activity, stability, and selectivity, such composites are significantly superior to known supported Pt-Co catalysts. Full article

Federated Learning (FL) provides a promising solution for preserving privacy in learning shared models on distributed devices without sharing local data on a central server. However, most existing work shows that FL incurs high communication costs. To address this challenge, we propose a clustering-based federated solution, entitled Federated Learning via Clustering Optimization (FedCO), which optimizes model aggregation and reduces communication costs. In order to reduce the communication costs, we first divide the participating workers into groups based on the similarity of their model parameters and then select only one representative, the best performing worker, from each group to communicate with the central server. Then, in each successive round, we apply the Silhouette validation technique to check whether each representative is still made tight with its current cluster. If not, the representative is either moved into a more appropriate cluster or forms a cluster singleton. Finally, we use split optimization to update and improve the whole clustering solution. The updated clustering is used to select new cluster representatives. In that way, the proposed FedCO approach updates clusters by repeatedly evaluating and splitting clusters if doing so is necessary to improve the workers’ partitioning. The potential of the proposed method is demonstrated on publicly available datasets and LEAF datasets under the IID and Non-IID data distribution settings. The experimental results indicate that our proposed FedCO approach is superior to the state-of-the-art FL approaches, i.e., FedAvg, FedProx, and CMFL, in reducing communication costs and achieving a better accuracy in both the IID and Non-IID cases. Full article

Proton-ceramic fuel cells (PCFCs) are promising devices for electrochemical energy conversion purposes due to their combination of high energy efficiency, environmental friendliness, and high durability. In the present work, the polarization characteristics of promising electrodes for PCFCs based on BaFe_xCe_0.7−xZr_0.2Y_0.1O_3−δ (BCZYFx) are comprehensively studied. Along with the individual BCZYFx electrodes, we investigated a method for improving their electrochemical activity by introducing nanoparticles of PrO_x electrocatalysts into the porous structure of the electrode material. According to the experimental data, electroactivation allowed for the polarization resistances of the electrodes at 700 °C to be reduced from 1.16, 0.27, 0.62 Ω°cm² to 0.09, 0.13, 0.43 Ω°cm² for x = 0.5, 0.6, and 0.7, respectively. For a PCFC cell with an air electrode of BCZYF0.6 composition activated using PrO_x nanoparticles, it was possible to achieve a maximum specific power of 300 mW cm⁻² at 750 °C, which is competitive for a single cell with Co-free cathodes. The results obtained provide insight into the processes occurring in the studied electrodes after electroactivation. It is shown how the improvement of electrochemical characteristics of the electrode can be realized by a simple infiltration method in combination with a subsequent thermal treatment. Full article

CuCe mixed oxide is one of the most studied catalytic systems for preferential CO oxidation (CO-PrOx) for the purification of hydrogen-rich gas stream. In this study, a series of ceria supports were prepared via a citrates-hydrothermal route by altering the synthesis parameters (concentration and temperature). The resulting supports were used for the preparation of CuCe mixed-oxide catalysts via wet impregnation. Various physicochemical techniques were utilized for the characterization of the resulting materials, whereas the CuCe oxide catalysts were assessed in CO-PrOx reaction. Through the proper modification of the hydrothermal parameters, CeO₂ supports with tunable properties can be formed, thus targeting the formation of highly active and selective catalysts. The nature of the reduced copper species and the optimum content in oxygen vacancies seems to be the key factors behind the remarkable catalytic performance of a CO-PrOx reaction. Full article

The thermal behaviour of Ag₂[PtCl₄] and Ag₂[PtCl₆] complex salts in inert and reducing atmospheres has been studied. The thermolysis of compounds in a helium atmosphere is shown to occur in two stages. At the first stage, the complexes decompose in the temperature range of 350–500 °C with the formation of platinum and silver chloride and the release of chlorine gas. At the second stage, silver chloride is sublimated in the temperature range of 700–900 °C, while metallic platinum remains in the solid phase. In contrast to the thermolysis of Ag₂[PtCl₆], the thermal decomposition of Ag₂[PtCl₄] at 350 °C is accompanied by significant heat release, which is associated with disproportionation of the initial salt to Ag₂[PtCl₆], silver chloride, and platinum metal. It is confirmed by DSC measurements, DFT calculations of a suggested reaction, and XRD. The thermolysis of Ag₂[PtCl₄] and Ag₂[PtCl₆] compounds is shown to occur in a hydrogen atmosphere in two poorly separable steps. The compounds are decomposed within 170–350 °C, and silver and platinum are reduced to a metallic state, while a metastable single-phase solid solution of Ag_0.67Pt_0.33 is formed. The catalytic activity of the resulting nanoalloy Ag_0.67Pt_0.33 is studied in the reaction of CO total (TOX) and preferential (PROX) oxidation. Ag_0.67Pt_0.33 enhanced Pt nano-powder activity in CO TOX, but was not selective in CO PROX. Full article

The preferential oxidation of CO (CO-PrOx) to CO₂ is an effective catalytic process for purifying the H₂ utilized in proton-exchange membrane fuel cells for power generation. Our current work reports on the synthesis, characterization and CO-PrOx performance evaluation of unsubstituted and magnesium-substituted iron- and cobalt-based oxide catalysts (i.e., Fe₃O₄, Co₃O₄, MgFe₂O₄ and MgCo₂O₄). More specifically, the ability of Mg to stabilize the MgFe₂O₄ and MgCo₂O₄ structures, as well as suppress CH₄ formation during CO-PrOx was of great importance in this study. The cobalt-based oxide catalysts achieved higher CO₂ yields than the iron-based oxide catalysts below 225 °C. The highest CO₂ yield (100%) was achieved over Co₃O₄ between 150 and 175 °C, however, undesired CH₄ formation was only observed over this catalyst due to the formation of bulk fcc and hcp Co⁰ between 200 and 250 °C. The presence of Mg in MgCo₂O₄ suppressed CH₄ formation, with the catalyst only reducing to a CoO-type phase (possibly containing Mg). The iron-based oxide catalysts did not undergo bulk reduction and did not produce CH₄ under reaction conditions. In conclusion, our study has demonstrated the beneficial effect of Mg in stabilizing the active iron- and cobalt-based oxide structures, and in suppressing CH₄ formation during CO-PrOx. Full article

The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H₂-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H₂ synergism under CO-PROX conditions on the low-index ceria surfaces (111), (110) and (100). Polycrystalline ceria, nanorods and ceria nanocubes were prepared to assess the physicochemical features of the targeted surfaces. Diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) shows that ceria surfaces are strongly carbonated even at room temperature by the effect of CO, with their depletion related to the CO oxidation onset. Conversely, formate species formed upon OH + CO interaction appear at temperatures around 60 °C and remain adsorbed regardless the reaction degree, indicating that these species do not take part in the CO oxidation. Density functional theory calculations (DFT) reveal that ceria facets exhibit high OH coverages all along the CO-PROX reaction, whilst CO is only chemisorbed on the (110) termination. A CO oxidation mechanism that explains the early formation of carbonates on ceria and the effect of the OH coverage in the overall catalytic cycle is proposed. In short, hydroxyl groups induce surface defects on ceria that increase the CO_x–catalyst interaction, revealed by the CO adsorption energies and the stabilization of intermediates and readsorbed products. In addition, high OH coverages are shown to facilitate the hydrogen transfer to form less stable HCO_x products, which, in the case of the (110) and (100), is key to prevent surface poisoning. Altogether, this work sheds light on the yet unclear CO–H₂ interactions on ceria surfaces during CO-PROX reaction, providing valuable insights to guide the design of more efficient reactors and catalysts for this process. Full article