i-LAB and Nano-Bionics Division, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences , Suzhou, Jiangsu, 215123, China.
ACS Nano. 2014 Apr 22;8(4):3724-34. doi: 10.1021/nn500386u. Epub 2014 Mar 10.
It is known that Co(OH)2 can be crystallized into a layered structure with two polymorphs: α and β. The single-layer α-Co(OH)2 nanosheet has been prepared by exfoliating directly α phase layered Co(OH)2. However, due to theoretical barriers, a single-layer β-Co(OH)2 nanosheet has not been achieved so far. In this article, phase transformation during exfoliation of layered Co(OH)2 from α to β is observed and a single-layer β-Co(OH)2 nanosheet with a thickness of ∼1.1 nm is prepared through phase transition of layered α-Co(OH)2 nanocones in a mild wet chemical process for the first time, with a nearly 100% yield. The as-prepared single-layer β-Co(OH)2 nanosheets are assembled with graphene oxide to form an all-two-dimensional materials-based composite for use as an electrode for the pseudocapacitor. The reduced graphene oxide/β-Co(OH)2 composite exhibits a high specific capacitance up to 2080 F/g scaled to the total mass of the electrode or 3355 F/g scaled to the active mass of β-Co(OH)2 nanosheets at the current density of 1 A/g. The electrode also demonstrates the excellent rate performance and long cycle life.
已知 Co(OH)2 可以结晶成具有两种多晶型物的层状结构：α 和 β。通过直接剥离α相层状 Co(OH)2 制备了单层α-Co(OH)2 纳米片。然而，由于理论障碍，目前尚未实现单层β-Co(OH)2 纳米片。在本文中，观察到层状 Co(OH)2 从α到β剥离过程中的相转变，并首次通过层状α-Co(OH)2 纳米锥在温和的湿化学过程中的相转变，以接近 100%的产率制备了厚度约为 1.1nm 的单层β-Co(OH)2 纳米片。所制备的单层β-Co(OH)2 纳米片与氧化石墨烯组装形成基于全二维材料的复合材料，用作赝电容器的电极。还原氧化石墨烯/β-Co(OH)2 复合材料在电流密度为 1A/g 时，其比电容高达 2080 F/g（相对于电极的总质量）或 3355 F/g（相对于β-Co(OH)2 纳米片的活性质量）。该电极还表现出优异的倍率性能和长循环寿命。
