Tuning the Anodic and Cathodic Dissolution of Gold by Varying the Surface Roughness

Abstract

This work presents the reactivity and dissolution of an aspolished and electrochemically pre-treated polycrystalline Au electrode, which is used as a model system. The effect of the electrochemical pre-treatment in corrosive 0.37 M HCl solutions on the Au surface roughness and dissolution is investigated by varying the number of pre-treatment steps at 1.16 V against the reversible hydrogen electrode. It is shown that the first 10 s pretreatment of the as-polished Au results in a higher surface roughness and thus higher electrochemically active surface area (ECSA) than that of the as-polished Au. With the subsequent pre-treatments, however, the ECSA is gradually decreasing reaching a steady value. The dissolution rate of the pre-treated Au electrodes upon potential cycling in 0.1 M H 2 SO 4 is determined by in situ inductively coupled plasma mass spec-trometry. A non-linear dependence of Au dissolution amount is found with respect to the number of pre-treatments. The overall total Au dissolution rate follows a similar trend as ECSA/ roughness. However, an important difference in the dissolution behavior is identified with respect to dissolution processes during Au oxidation (anodic dissolution) and Au reduction (cathodic dissolution): the former is more sensitive to the surface roughness. Thus, the ratio between Au anodic and cathodic dissolution amounts decreases substantially with decrease in surface roughness. This finding is explained by the slow and fast dissolution kinetics for anodic and cathodic processes, respectively. Current work further advances our understanding of the complex Au dissolution mechanism.

Natural corrosion-induced gold nanoparticles yield purple color of Alhambra palaces decoration

“…Corrosion of the Au leaf is assisted by its thinness ( 32 ), roughness ( 16 ), and Ag content ( 5 , 33 ). Corrosion is further enhanced by the Cl − -rich environment ( 27 ).…”

“…In closing, the electrochemical oxidation/dissolution of Au is a complex subject usually studied under laboratory conditions using ad hoc equipment, methods, and thermodynamic approaches ( 16 , 39 ). Conversely, here, we propose a pioneering robust model that sheds light on the degradation of bimetallic artistic gilding, including Au dissolution and AuNP precipitation under natural conditions in a Cl − -rich medium.…”

“…Although Au is said to be corrosion free, we know that Au can dissolve in aqua regia (1:3 molar mixture of HNO 3 to HCl) and, for instance, in mixture solutions that yield chlorine (Cl) or are NaCl saturated at room temperature ( 1 , 2 , 15 , 16 ). Certainly, Au can be reactive in diverse conditions provided that a strong oxidant and a complexing ligand for Au cations are present ( 1 , 2 , 17 ).…”

Electrochemical Cleaning Stability and Oxygen Reduction Reaction Activity of 1‐2 nm Dendrimer‐Encapsulated Au Nanoparticles

“…[7,8,57,58] Indeed, it has been shown that polycrystalline Au can undergo potential-dependent anodic dissolution via a variety of mechanisms under acidic conditions, especially for electrodes having a high roughness factor. [23,57,58,87] There is evidence from both theory and experiment that this dissolution is more pronounced for AuNPs smaller than 1.5 nm. [4,7,8,24,60,61,88] The foregoing literature studies of Au dissolution at positive potentials are directly relevant to our interpretation of the results in the present study.…”

“…[7,8,13,16,[20][21][22] Even for polycrystalline gold surfaces, the rate of anodic Au dissolution during potential cycling is highly dependent on the surface structure of the electrode. [23] These atomic-level structural changes are further exacerbated for very small (<~5 nm) NPs due to their inherent instability. [24][25][26][27] The foregoing problems are further compounded by the fact that in some cases electrocatalytic NPs are only characterized immediately after synthesis, less frequently after catalysis, and generally not at all during or after cleaning protocols.…”