Deng Bing, Wang Zhe, Chen Weiyin, Li John Tianci, Luong Duy Xuan, Carter Robert A, Gao Guanhui, Yakobson Boris I, Zhao Yufeng, Tour James M
Department of Chemistry, Rice University, Houston, TX, 77005, USA.
Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA.
Nat Commun. 2022 Jan 11;13(1):262. doi: 10.1038/s41467-021-27878-1.
Nanoscale carbides enhance ultra-strong ceramics and show activity as high-performance catalysts. Traditional lengthy carburization methods for carbide syntheses usually result in coked surface, large particle size, and uncontrolled phase. Here, a flash Joule heating process is developed for ultrafast synthesis of carbide nanocrystals within 1 s. Various interstitial transition metal carbides (TiC, ZrC, HfC, VC, NbC, TaC, CrC, MoC, and WC) and covalent carbides (BC and SiC) are produced using low-cost precursors. By controlling pulse voltages, phase-pure molybdenum carbides including β-MoC and metastable α-MoC and η-MoC are selectively synthesized, demonstrating the excellent phase engineering ability of the flash Joule heating by broadly tunable energy input that can exceed 3000 K coupled with kinetically controlled ultrafast cooling (>10 K s). Theoretical calculation reveals carbon vacancies as the driving factor for topotactic transition of carbide phases. The phase-dependent hydrogen evolution capability of molybdenum carbides is investigated with β-MoC showing the best performance.
纳米级碳化物增强了超强陶瓷，并展现出作为高性能催化剂的活性。传统用于碳化物合成的冗长渗碳方法通常会导致表面结焦、颗粒尺寸大以及相难以控制。在此，开发了一种闪速焦耳加热工艺，用于在1秒内超快合成碳化物纳米晶体。使用低成本前驱体可制备各种间隙过渡金属碳化物（TiC、ZrC、HfC、VC、NbC、TaC、CrC、MoC和WC）以及共价碳化物（BC和SiC）。通过控制脉冲电压，可选择性地合成包括β-MoC以及亚稳α-MoC和η-MoC在内的相纯碳化钼，这表明闪速焦耳加热具有出色的相工程能力，其能量输入可广泛调节，能超过3000 K，同时具备动力学控制的超快冷却（>10 K s）。理论计算表明碳空位是碳化物相拓扑转变的驱动因素。研究了碳化钼的相依赖析氢能力，其中β-MoC表现出最佳性能。
