Influence of Composite Additive on Gold Electrodeposition in DMH-Based Electrolyte: Combined Experimental and Theoretical Study

Abstract

The comparison of macroscopic appearance and microscopic morphology of gold electrodeposit determined PHEN as the main brightener for its effective influence on refining the grains, resulting in a golden bright and shiny deposit. Improving the flatness of deposit when used together with PHEN, PDDA was the auxiliary brightener, thereby obtaining thicker deposits. Results of TEM and XRD showed that the average size of refined gold crystals was about 20 nm. We speculated from the patterns of XPS that the action of the additive molecule is to adsorb on the metal surface. Combined electrochemical measurements and MD simulations revealed that both PHEN and PDDA molecules could steadily adsorb on the surface of Ni and Au, increasing the polarization of the cathode surface and promote the refinement of grains. PHEN was the main additive when used as a composite additive for its higher adsorption energy than PDDA. The effective adsorption of PHEN and PDDA molecules led to the enhancement of cathodic polarization, causing the negative shift of potential and the decrease of current in cyclic voltammetry of the second step reduction. The chronoamperometry measurements indicated that the nucleation process was a progressive model. The grain growth was significantly inhibited when the additives were used.

Toward Stable Zinc-Ion Batteries: Use of a Chelate Electrolyte Additive for Uniform Zinc Deposition

“…Contact angle measurements indicated that the electrolytes with EDTA had an enhanced affinity for Zn (Figure e). DFT calculations also revealed that the functional groups of EDTA endowed the EDTA on the Zn foil with a good adsorption capability (Figure f), thus ensuring an abundance of activated sites that would contribute to the generation of refined nucleation grains with good uniformity . Moreover, foreign adsorbed molecules on the surface of electrode can improve the activation energy for adatoms diffusion, thus restraining the 2D surfacial ion diffusion, which may lead to dendrite growth …”

Suppressing Sulfite Dimerization at a Polarized Gold Electrode/Water Solution Interface for High-Quality Gold Electrodeposition

“…The intricate electrochemical reactions led to the adsorption of S 2 O 5 2– and S 2 O 3 2– on the cathode. Tu et al pointed out that the interfacial adsorbate significantly affected the morphology, appearance of coating, and the performance of the bath during the metal ions electroreduction. It can be clearly seen that the adsorption of S 2 O 5 2– and S 2 O 3 2– will influence the quality of coating in metal (such as gold) sulfite electrodeposition.…”

“…the cathode. Tu et al26 pointed out that the interfacial adsorbate significantly affected the morphology, appearance of coating, and the performance of the bath during i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d . the metal ions electroreduction.…”