Han Ye-Chuang, Liu Meng-Li, Sun Li, Li Shuxing, Li Gen, Song Wei-Shen, Wang Yan-Jie, Nan Zi-Ang, Ding Song-Yuan, Liao Hong-Gang, Yao Yonggang, Stucky Galen D, Fan Feng Ru, Tian Zhong-Qun
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province, Xiamen University, Xiamen 361005, China.
College of Materials, Xiamen University, Xiamen 361005, China.
Proc Natl Acad Sci U S A. 2022 Sep 13;119(37):e2121848119. doi: 10.1073/pnas.2121848119. Epub 2022 Sep 6.
Refractory carbides are attractive candidates for support materials in heterogeneous catalysis because of their high thermal, chemical, and mechanical stability. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered by their low surface area and harsh synthetic conditions, typically have a very limited surface area (<200 m g), and are prepared in a high-temperature environment (>1,400 °C) that lasts for several or even tens of hours. Based on Le Chatelier's principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction (CR) strategy was capable of synthesizing high-surface area SiC (569.9 m g) at a lower temperature and a faster rate (∼1,300 °C, 50 Pa, 30 s). Such high-surface area SiC possesses excellent thermal stability and antioxidant capacity since it maintained stability under a water-saturated airflow at 650 °C for 100 h. Furthermore, we demonstrated the feasibility of our strategy for scale-up production of high-surface area SiC (460.6 m g), with a yield larger than 12 g in one experiment, by virtue of an industrial viable vacuum sintering furnace. Importantly, our strategy is also applicable to the rapid synthesis of refractory metal carbides (NbC, MoC, TaC, WC) and even their emerging high-entropy carbides (VNbMoTaWC, TiVNbTaWC). Therefore, our low-pressure CR method provides an alternative strategy, not merely limited to temperature and time items, to regulate the synthesis and facilitate the upcoming industrial applications of carbide-based advanced functional materials.
难熔碳化物因其高的热稳定性、化学稳定性和机械稳定性，是多相催化中载体材料的理想候选物。然而，难熔碳化物，尤其是碳化硅（SiC）的工业应用，因其低比表面积和苛刻的合成条件而受到极大阻碍，其比表面积通常非常有限（<200 m²/g），且是在持续数小时甚至数十小时的高温环境（>1400°C）中制备的。基于勒夏特列原理，我们从理论上提出并通过实验验证了一种低压碳热还原（CR）策略能够在较低温度和更快的速率（~1300°C，50 Pa，30 s）下合成高比表面积的SiC（569.9 m²/g）。这种高比表面积的SiC具有优异的热稳定性和抗氧化能力，因为它在650°C的水饱和气流下保持稳定100小时。此外，借助工业上可行的真空烧结炉，我们证明了我们的策略用于大规模生产高比表面积SiC（460.6 m²/g）的可行性，一次实验的产量大于12 g。重要的是，我们的策略也适用于难熔金属碳化物（NbC、MoC、TaC、WC）甚至其新兴的高熵碳化物（VNbMoTaWC、TiVNbTaWC）的快速合成。因此，我们的低压CR方法提供了一种替代策略，不仅限于温度和时间方面，以调节合成并促进基于碳化物的先进功能材料即将到来的工业应用。
