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Catalytic oxidation of carbon monoxide (CO) is an important step in purifying automobile exhaust or preferentially oxidizing CO in a hydrogen atmosphere. Designing high-performance CO low-temperature oxidation catalysts is of great significance to energy conservation, environmental protection and human health. Through the study of the mechanism and technology of CO low-temperature oxidation, we can find solutions to design efficient active sites and promote the development of related fields.
The main point of this paper
Importance of CeO2 catalysts:
CeO2 has been widely studied for its ability to provide and store oxygen under different oxygen conditions, which is mainly attributed to the conversion between Ce3+ and Ce4+ and the generation of oxygen vacancies, thereby enhancing the oxidation of CO.
Synthesis of CeO2 and ZrO2 nanospheres:
Pandit and Ahmad synthesized CeO2 and ZrO2 nanospheres using a hydrothermal method, and these materials have become candidates for high-performance gas sensors due to their excellent gas sensing capabilities.
Catalytic effect of copper (Cu):
Copper is an active metal with three different valence states, and its oxides show high activity at low temperatures. The easy electron transfer of copper leads to the change of the oxide valence state, which affects the release or capture of oxygen molecules to form oxygen vacancies.
Interaction between CuO and CeO2:
The efficiency of the catalyst is related to the interaction of the interfacial sites between CuO and CeO2, which is related to the oxidation of CO and the redox cycles of the abundant Ce4+/Ce3+ and Cu2+/Cu+ at the interface of copper and cerium.
Limitations of traditional preparation methods:
Traditional methods for preparing Cu/CeO2-based catalysts include impregnation and sol-gel methods, but it is still difficult to precisely control the position of Cu nanoparticles in the CeO2 carrier, and the performance and stability of the catalyst are limited by gas diffusion and electron transfer rates.
Advantages of electrospinning technology:
Electrospinning technology is used to make nanofiber catalysts, which have greater porosity, promote gas diffusion, and the active components are evenly distributed in the catalyst, which is conducive to electron transfer. This technology can prepare porous nanomaterials with high specific surface area and control the morphology and structure of the catalyst.
Importance:
The use of non-precious metal catalysts to eliminate CO emissions is essential for environmental protection.
Challenges of Cu-based catalysts:
Cu-based catalysts are widely used in CO oxidation, but their activity and stability at low temperatures are a challenge.
Preparation and performance of novel catalysts:
This paper reports a highly efficient copper-doped cerium fiber catalyst prepared by electrospinning technology.
The 10Cu-Ce fiber catalyst can achieve complete CO oxidation at temperatures as low as 90°C, while the 10Cu/Ce catalyst prepared by the traditional impregnation method requires 110°C.
Mechanism of enhanced interfacial activity:
Asymmetric oxygen vacancies (ASOVs) are constructed at the interface between copper and cerium, which can effectively absorb gas molecules involved in the reaction and enhance CO oxidation.
Special adsorption capacity:
The special adsorption capacity of 10Cu-Ce catalyst for CO is attributed to its unique structure and surface interactions, especially the Cu+-Ov-Ce3+ sites.
Characterization and theoretical verification:
The special performance of 10Cu-Ce catalyst is demonstrated by a series of characterizations and density functional theory (DFT) calculations.
In this paper, a series of copper-doped ceria electrospun fibers were successfully synthesized by electrospinning. Fibers with different copper contents were synthesized, and complete CO conversion was achieved at a low temperature of 90°C in the presence of 10% Cu-Ce catalyst. By changing the preparation method to the traditional impregnation method, 10% Cu/Ce required a higher temperature (110°C) to completely convert CO. The results show that directly doped spun fibers can expose more oxygen vacancies and have stronger adsorption capacity for active gas molecules compared with supported catalysts with the same copper content. In addition, electrospinning promotes the dispersion of active sites, making it possible to decorate the nanofibers with heteroatoms and CeO2 species in situ. This embedded structure enhances the generation of Cu+-Ov-Ce3+ active sites at the interface, resulting in efficient dynamic charge balance. Through various characterizations, we summarize the effects of copper doping on the catalytic performance and identify obstacles and potential solutions for the widespread application of copper-cerium catalysts. This work proposes future research and development directions for the preparation of efficient non-precious metal-based catalysts for various catalytic reactions.
