CuFe_x/CeO₂ Catalysts Prepared by Sol-Gel Method for Low-Temperature Catalytic CO Oxidation AITranslate

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Basic Information:

DOI：10.13373/j.cnki.cjrm.XY25050003

Chinese Library Classification Number:O643.3

Citation Information:

Carbon monoxide (CO) is a colorless, odorless, and highly toxic gas, primarily produced by vehicle emissions and incomplete fossil fuel combustion. It poses significant environmental risks and binds to hemoglobin in the bloodstream, leading to hypoxia. Catalytic oxidation is an efficient and energy-saving method for CO removal. Noble metal catalysts, such as Pd-based and Pt-based systems, demonstrate excellent activity for CO oxidation, though their high cost hinders large-scale industrial application. Thus, developing non-noble metal catalysts that enable complete CO oxidation at low temperatures is crucial. The sol-gel method, a versatile wet-chemical synthesis technique, allows precise control over catalyst composition and microstructure, ensuring highly uniform dispersion of active components on the support. In this work, a series of trimetallic 5%CuFe_x/CeO₂ (x=0~0.1) catalysts with controlled Fe doping were prepared via sol-gel method to elucidate the promotional effect of Fe on Cu/CeO₂ for low-temperature CO oxidation. Comprehensive characterization including X-ray diffraction (XRD), Raman, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) was conducted to probe the catalysts' structural, textural, and electronic properties. H₂-temperature-programmed reduction (H₂-TPR), O₂-temperature-programmed desorption (O₂-TPD), and CO-temperature-programmed desorption (CO-TPD) were used to elucidate the redox capacity of the catalyst and the activation of reactant molecules CO and O₂.The catalytic evaluation demonstrated that 5%CuFe_0.025/CeO₂ catalyst showed optimal performance, achieving 100% CO conversion at 70 ℃, which represented a significant 40% improvement in low-temperature activity compared to the Fe-free Cu/CeO₂ reference catalyst. Furthermore, the catalyst exhibited excellent stability, maintaining complete CO conversion throughout a 60 h stability test. XRD patterns confirmed the preservation of CeO₂ fluorite structure in all catalysts, with no detectable CuO_x or FeO_x crystalline phases, suggesting the high dispersion of both Cu and Fe species on the catalyst surface. SEM and N₂ physisorption analysis revealed that the sol-gel synthesized 5%CuFe_x/CeO₂ catalysts possessed a hierarchical porous architecture. Fe incorporation promoted the formation of an interconnected network-like morphology with uniform pore distribution, increasing the specific surface area, which optimized texture and facilitates mass transport while maximizing active site accessibility, significantly enhancing reaction kinetics. Raman spectroscopy analysis demonstrated that Fe doping modifies metal-oxygen bond lengths, creating additional oxygen vacancies. These defect sites facilitated oxygen activation from ambient air, generating reactive oxygen species for CO oxidation. Supporting evidence from O₂-TPD revealed a distinct low-temperature shift in oxygen desorption peaks after Fe incorporation, while XPS analysis of O 1s spectra confirmed the increased abundance of reactive oxygen species-both findings corroborating the enhanced oxygen activation capacity induced by Fe doping. H₂-TPR analysis revealed enhanced α-peak hydrogen consumption with increasing Fe loading, indicating improved oxygen mobility. Combined CO-TPD and XPS characterizations demonstrated that optimal Fe doping promotes CuO_x dispersion and increases the concentration of active Cu⁺ sites for CO chemisorption. However, excessive Fe loading (x=0.1) led to attenuated CO desorption intensity in TPD profiles, suggesting iron oxide over-deposition may block active sites and reduce CO adsorption capacity. In-situDRIFTS analysis revealed a carbonate-mediated Mars-van Krevelen (M_V-K) mechanism for CO oxidation over the catalyst. As the reaction temperature rose, the abundance of Cu⁺-CO species increased, accompanied by enhanced peaks corresponding to carbonate intermediates. This suggested that adsorbed CO reacted with surface-active oxygen species to form carbonate species, which subsequently decomposed into CO₂ and desorbed from the catalyst surface. The vacant oxygen sites were then replenished by adsorbed O₂ from the gas phase, generating new active oxygen species. These reactive oxygen species reacted with adjacent adsorbed CO to produce additional CO₂, completing the catalytic cycle. These results indicated that the catalytic performance of copper-cerium catalysts for complete CO oxidation could be significantly improved by strategically doping trace metal additives, thereby enabling completed CO conversion at lower operating temperatures.