Department of Chemistry, American University of Beirut, P.O.Box 11-0236, Riad El-Solh 1107 2020, Beirut, Lebanon.
J Phys Chem A. 2013 Feb 28;117(8):1685-91. doi: 10.1021/jp308354f. Epub 2013 Feb 18.
A new and simple method is proposed to explore the mechanism of the intercalation/deintercalation of a variety of anions throughout the formation of α-Co(OH)2 crystals and their polymorphic conversion to β-Co(OH)2. This method is based on the reaction-diffusion of hydroxide ions in a gel matrix containing the cobalt salt. The spatiotemporal evolution of each polymorph and their interaction is revealed by tracking the location of the two sharp interfaces between the two polymorphs (conversion zone) and between the gel and α-Co(OH)2 (formation zone) and by measuring the weight composition of each zone. We thereby find that the dynamics of the transformation reaction are correctly described by the two-dimensional Avrami-Erofe'ev equation at different temperatures. The data suggest that the structural redistribution of the atoms inside the α-Co(OH)2 particles plays the fundamental role in establishing the overall rate of the reaction. On the other hand, we notice that other factors such as the nature of the intercalated anions and the concentration of the polymer matrix alter considerably the final rate of the transition reaction through increasing the stability of the α phase.
提出了一种新的简单方法，用于探索各种阴离子在α-Co(OH)2 晶体形成过程中的嵌入/脱嵌机制及其向β-Co(OH)2 的多晶型转化。该方法基于包含钴盐的凝胶基质中氢氧根离子的反应扩散。通过跟踪两种多晶型体（转化区）之间以及凝胶和α-Co(OH)2 之间的两个尖锐界面（形成区）的位置，并测量每个区的重量组成，揭示了每个多晶型体及其相互作用的时空演化。因此，我们发现，在不同温度下，转换反应的动力学可以通过二维 Avrami-Erofe'ev 方程正确描述。数据表明，α-Co(OH)2 颗粒内部原子的结构再分配在确定反应的整体速率方面起着根本作用。另一方面，我们注意到，嵌入阴离子的性质和聚合物基质的浓度等其他因素通过增加α相的稳定性，极大地改变了过渡反应的最终速率。
