Determination of the Diffusion-Adsorption Properties of Polymeric Electrolyte Additives Using an Additive Injection Method Implemented on a Rotating Disc Electrode

• Published in: Journal of the Electrochemical Society 2016-01, Vol.163 (9), p.E241-E247
• Main Authors: Banik, Stephen J., Rao, Karun K., Akolkar, Rohan
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.0231609jes

The diffusion and adsorption properties of an electrolyte additive polyethylenimine (PEI), employed during zinc (Zn) electrodeposition, are characterized via additive injection experiments implemented on a rotating disc electrode (RDE). Under galvanostatic Zn electrodeposition on a RDE, the transient response of the electrode potential upon PEI injection into the electrolyte is measured. The electrode potential response is indicative of the gradual adsorption of PEI on the electrode surface and thus provides an adsorption time constant. The measured adsorption time constant is analyzed using a transient diffusion-adsorption model, which leads to the determination of the PEI diffusion coefficient (DPEI) and its surface-limited adsorption rate constant (kads). Analysis confirms that PEI adsorption during Zn electrodeposition is limited by its slow diffusion and not by the fast kinetics of surface adsorption. The additive injection method implemented herein provides a convenient metrology for characterizing the diffusion and adsorption properties of polymeric additives used in numerous electrodeposition systems, while providing insights into the rate-limiting processes that govern additive adsorption during electrodeposition.