Electromicrogravimetric study of underpotential deposition of Co on textured gold electrode in ammonia medium
作者:Antonio Montes-Rojas、Luz María Torres-Rodríguez、Cesar Nieto-Delgado
DOI:10.1039/b704891b
日期:——
Formation of a layer of a metal M on a foreign metal substrate, S, at potentials positive to its reversible potential, Er, (underpotential deposition, UPD) is a phenomenon that appears only in some systems. In the case of the UPD process of Co on a gold substrate, there is still a controversy about its existence, for which reason, in this study, voltammetry and chronoamperometry were coupled with a quartz microbalance in ammonium solution to better understand its formation mechanism. The results obtained show that the Co forms only one layer on the substrate before the bulk deposition of cobalt occurs. During the UPD process, the Co atom completely transfers its two electrons to the electrode and is adsorbed as a discharged species. The monolayer charge density, determined by electromicrogravimetry, is 448 μC cm−2 and probably corresponds to a commensurate overlayer on the gold substrate. In addition, the UPD process is controlled by adsorption as shown by voltammetric experiments. Finally, the analysis of the process of Co monolayer destruction (desorption) shows a mechanism different from that in the formation process, possibly due to H adsorption on the substrate produced during the process of adsorption of Co.
在外来金属基底 S 上形成一层金属 M,其电位正于其可逆电位 Er(电位不足沉积,UPD),这种现象只出现在某些体系中。在本研究中,伏安法和计时器与石英微天平在铵溶液中结合使用,以更好地了解其形成机制。研究结果表明,钴在基底上只形成一层,然后才开始大量沉积。在 UPD 过程中,钴原子将其两个电子完全转移到电极上,并作为放电物种被吸附。通过电化学重力测量法测定的单层电荷密度为 448 μC cm-2,可能与金基底上的相称覆盖层相对应。此外,伏安法实验表明,UPD 过程受吸附控制。最后,对 Co 单层破坏(解吸)过程的分析表明,其机制与形成过程不同,可能是由于在吸附 Co 的过程中基底上产生了 H 吸附。