Theoretical and experimental studies on the electrodeposited nanocrystalline Ag coatings from a novel Ag₂O-based non-cyanide electrolyte

Functional silver coatings have been widely applied in fields of electrochemical energy conversion systems, electronics industry and antibacterial materials, and exploiting new non-cyanide silver electroplating bath system is of great significance for promoting the application. In this work, a new type of cyanide-free electrodeposited silver (Ag) system was developed with Ag₂O as the main salt, 5,5-dimethyl hydantoin (DMH) as the silver ion complexing agent and potassium carbonate as the conductive salt. Comprehensive quantum chemical calculations demonstrate that the new silver-based system has the solvation structure of [Ag(C₅H₇N₂O₂)₂]⁻(5N(2)-Ag). To further, roles of additives combination (L-cysteine and 2,2-bipyridine) and their fundamental mechanism on the silver electrodeposition process was further investigated by electrochemical tests and theoretical calculations. First-Principles calculation and simulation of molecular dynamics reveal that this additive couple have coordination interactions with Ag⁺, while strong adsorption on the Ag (1 1 1) surface. SEM and XRD analyses showed that the combination of L-cysteine and 2,2-bipyridine achieved an ideal silver coating with good morphology and a low grain size of 22.1 nm, verifying the great potential of the novel system to prepare high-quality silver coatings.