The Role of Water Content of Deep Eutectic Solvent Ethaline in the Anodic Process of Gold Electrode

• Published in: Molecules (Basel, Switzerland) Vol. 28; no. 5; p. 2300
• Main Authors: Wu, Jie-Du, Ding, Yu, Zhu, Feng, Gu, Yu, Wang, Wei-Wei, Sun, Lan, Mao, Bing-Wei, Yan, Jia-Wei
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.03.2023; MDPI
• Subjects: Anodic dissolution; Atomic force microscopy; Chloride; deep eutectic solvents; Dissolution; electrochemical etching; Electrochemical impedance spectroscopy; Electrochemistry; Electrodes; Electrolytes; Electron transfer; Etching; ethaline; Gold; Hydrogen bonds; Interfaces; Iodine; Microelectromechanical systems; Moisture content; passivation; Phase transitions; Solvents; Spectroscopy; Spectrum analysis; VOCs; Volatile organic compounds; Water; Water content; water content; electrochemical etching; passivation; anodic dissolution; deep eutectic solvents; ethaline
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28052300

Traditional coupling of ligands for gold wet etching makes large-scale applications problematic. Deep eutectic solvents (DESs) are a new class of environment-friendly solvents, which could possibly overcome the shortcomings. In this work, the effect of water content on the Au anodic process in DES ethaline was investigated by combining linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Meanwhile, we employed atomic force microscopy (AFM) to image the evolution of the surface morphology of the Au electrode during its dissolution and passivation process. The obtained AFM data help to explain the observations about the effect of water content on the Au anodic process from the microscopic perspective. High water contents make the occurrence of anodic dissolution of gold at higher potential, but enhances the rate of the electron transfer and gold dissolution. AFM results reveal the occurrence of massive exfoliation, which confirms that the gold dissolution reaction is more violent in ethaline with higher water contents. In addition, AFM results illustrate that the passive film and its average roughness could be tailored by changing the water content of ethaline.