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Research Background and Significance
Catalyst sintering problem: Even at low temperatures of 80°C, metal catalysts (especially ultrafine nanoparticles < 3 nm) sinter due to high surface energy, leading to reduced active sites and limited high-temperature applications (such as automotive exhaust treatment, chemical reactions).
Traditional carrier defects: Conventional oxide carriers (CeO2), (TiO2), (Fe2O3) can alleviate sintering but are prone to structural collapse under long-term high temperatures, with insufficient stability; traditional regeneration methods (such as chlorination) require precise control of temperature and chlorine concentration, making the process complex.
HEO potential: High-entropy oxides utilize high configurational entropy effects to construct stable structures and provide complex surface chemical environments, offering new solutions for the dispersion and stability of metal species.
Figure 1. Structural characterization of (CrMnFeCoZnMg0.5)3O4 high-entropy oxide nanofibers.
Recently, Professor Dai Yunqian's team at Southeast University studied porous high-entropy oxide (HEO) nanofibers, utilizing their unique high-entropy effect to promote the self-regeneration of sintered Pt. The high configurational entropy in Pt/HEO enabled Pt nanoparticles to redisperse from 5.8 nm (after sintering at 900°C) to 3.4 nm through simple low-temperature heat treatment at 500°C, which was also verified by in situ HAADF-STEM. The self-regenerated Pt/HEO-900-500°C almost completely recovered CO oxidation performance, with the T50 (50% conversion temperature) only increasing by 4°C compared to the original Pt/HEO. Particularly, Pt/HEO-900-500°C exhibited a low deactivation rate constant of 4.7 × 10−3 h−1 over 85 hours in CO oxidation. The related research results were published under the title "Entropy-Driven Self-Regeneration of Ultrafine Pt on Porous High-Entropy Oxide Nanofibers" in the journal Advanced Functional Materials.
Figure 2. (a) Morphological and structural characterization of Pt/HEO (platinum/high-entropy oxide).
Figure 3. In situ high-angle annular dark-field scanning transmission electron microscopy observations of platinum/high-entropy oxide (Pt/HEO) after aging under different conditions.
Figure 4. (a) Carbon monoxide (CO) oxidation performance of platinum/high-entropy oxide (Pt/HEO) under different high-temperature conditions. (b), (c) CO oxidation performance of platinum/low-entropy oxides under different high-temperature conditions. (d), (e) CO oxidation performance of platinum/medium-entropy oxides under different high-temperature conditions. (f) 50% conversion temperature (T50) of platinum/low-entropy oxides, platinum/medium-entropy oxides, and platinum/high-entropy oxide (Pt/HEO) under different high-temperature conditions. (g) Stability of Pt/HEO-900-500°C (Pt/HEO treated at 500°C after sintering at 900°C) in CO oxidation reactions. (h) Comparison of deactivation rates between catalysts in this study and other Pt-based catalysts in CO oxidation reactions.
Conclusion
To enhance the thermal stability and regeneration capacity of supported catalysts, this study utilizes the high configurational entropy effect to promote the redispersion of platinum (Pt) species on high-entropy oxide (HEO) nanofibers. Through secondary heat treatment, entropy-driven reconstruction of sintered platinum nanoparticles can be achieved without additional chemical agents: after annealing at 900°C in a nitrogen environment, platinum nanoparticle size increased to 5.8 nm, while reheating to 500°C reduced the size to 3.4 nm, confirming the regeneration capability of the Pt/HEO system.
In carbon monoxide (CO) oxidation performance tests, the regenerated Pt/HEO-900-500°C (Pt/HEO treated at 500°C after sintering at 900°C) demonstrated restored catalytic performance, with its 50% conversion temperature (T50) only 4°C higher than the original Pt/((CrMnFeCoZnMg0.5)3O4). Furthermore, under continuous operation at approximately 52% CO conversion, the catalyst exhibited excellent thermal stability—a deactivation rate constant as low as 4.7×10⁻³ h⁻¹ over 85 hours of operation, indicating outstanding resistance to decay in the CO oxidation reaction. These findings provide a new approach for analyzing the redispersion behavior of supported metal catalysts and for designing anti-sintering catalysts with enhanced thermal stability.
