关键词: 低共熔溶剂, 氧化锌, 电化学, 还原, 锌

Abstract:

The effect of ZnO concentration on the electrochemical behaviors of ChCl-urea-ZnO deep eutectic solvents (DES) system were examined with electric conductivity tests and cyclic voltammetry. The results of electric conductivity tests indicate that the conductivity of ChCl-urea-ZnO DES increases with an increase in ZnO concentration as ZnO concentration is below 0.24 mol·L^-1. When ZnO concentration exceeds 0.24 mol·L^-1, the conductivity of ChCl-urea-ZnO DES tends to be roughly constant. The conductivity of ChCl-urea-ZnO DES increases with the increasing of temperature. The relation between conductivity and temperature is consistent with Kohlraush empirical formula. The results of voltammetry tests indicate that the reduction of Zn(Ⅱ) is a quasi-reversible process, which is controlled by diffusion step. The diffusion coefficient of zinc ion is about 1.2×10^-7 cm²·s^-1. Furthermore, with an increase in ZnO concentration, deposition potential of Zn shifts positively and reduction peak current increases gradually, indicating that the higher concentration of ZnO is helpful to the electrodeposition of zinc. In addition, the electrodeposition of Zn-ChCl-urea DES containing different concentration of ZnO was performed at 2.2 V and 343 K. The surface morphology and phase structure of Zn deposits were characterized by X-ray diffraction (XRD) and scanning electron microscopic (SEM), respectively. ZnO concentration is found to play central role on the morphology of deposited Zn. Different shapes of Zn deposits including rod-like and square, can be electrodeposited from ChCl-urea DES by controlling the ZnO concentration.

Key words: deep eutectic solvents, zinc oxide, electrochemistry, reduction, znic