Fu Wanlin, Yu Ying, Yin Kuibo, Li Zhihui, Tang Mingyu, Tian Jilan, Wei Guanzhao, Zhou Shiming, Sun Yueming, Dai Yunqian
School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, P. R. China.
SEU-FEI Nano-Pico Center, Key Laboratory of MEMS of Ministry of Education, Southeast University, Nanjing 211189, P. R. China.
ACS Appl Mater Interfaces. 2024 Sep 11;16(36):47513-47523. doi: 10.1021/acsami.4c08126. Epub 2024 Aug 13.
Ultrafine noble metals have emerged as advanced nanocatalysts in modern society but still suffer from unavoidable sintering at temperatures above 250 °C (e.g., Pt). In this work, closely packed CeO grains were confined elegantly in fibrous nanostructures and served as a porous support for stabilizing sub-3 nm Pt clusters. Through precisely manipulating the asymmetry of obtained nanofibers, uneven strain was induced within C-shaped CeO nanofibers with tensile strain at the outer side and compressive strain at the inner side. As a result, the enriched oxygen vacancies significantly improved adhesion of Pt to CeO, thereby boosting the sinter-resistance of ultraclose sub-3 nm Pt clusters. Notably, no aggregation was observed even after exposure to humid air at 750 °C for 12 h, which is far beyond their Tammann temperature (sintering onset temperature, below 250 °C). HAADF-STEM observation revealed a unique sintering mechanism, wherein Pt clusters initially migrate toward the grain boundaries with concentrated stain and undergo slight coalescence, followed by subsequent Ostwald ripening at higher temperatures. Moreover, the sinter-resistant Pt/C-shaped CeO effectively catalyzed soot combustion (over 700 °C) in a durable manner. This work provides a new insight for developing sinter-resistant catalysts from the perspective of strain engineering within nano-oxides.
超细贵金属已成为现代社会中的先进纳米催化剂，但在高于250°C的温度下（如铂）仍不可避免地会发生烧结。在这项工作中，紧密堆积的CeO晶粒被巧妙地限制在纤维纳米结构中，并作为稳定亚3纳米铂簇的多孔载体。通过精确控制所得纳米纤维的不对称性，在C形CeO纳米纤维内部诱导出不均匀应变，外侧为拉伸应变，内侧为压缩应变。结果，富集的氧空位显著提高了铂与CeO的附着力，从而增强了超紧密亚3纳米铂簇的抗烧结性。值得注意的是，即使在750°C的潮湿空气中暴露12小时后也未观察到团聚现象，这远远超过了它们的坦曼温度（烧结起始温度，低于250°C）。高角度环形暗场扫描透射电子显微镜（HAADF-STEM）观察揭示了一种独特的烧结机制，其中铂簇最初向应变集中的晶界迁移并经历轻微聚结，随后在更高温度下发生奥斯特瓦尔德熟化。此外，抗烧结的Pt/C形CeO以持久的方式有效地催化了烟灰燃烧（超过700°C）。这项工作从纳米氧化物内的应变工程角度为开发抗烧结催化剂提供了新的见解。
