Structural Evolution of Au Electrodes during Cathodic Corrosion: Initial Stages of Octahedral-Nanocrystal Growth

Abstract

Cathodic corrosion of Au wires in highly concentrated NaOH (5-20 M) is systemically investigated to monitor the structural transformation as a function of applied electrode potential, polarization time, and electrolyte concentration. Current -potential curves for the restructured Au electrodes in 0.1 M H2SO4 demonstrate preferential (111)-orientation of nanofacets and an increase in electrochemically active surface area as a function of the applied parameters. Scanning electron microscopy shows that polarizing the Au surfaces at sufficiently negative potentials leads to the growth of nanosized octahedral and triangular crystallites that can be tailored by varying NaOH concentrations. The nanocrystal growth occurs through dissolution and metal redeposition. The formation of etching pits indicates that Au dissolution is dominating during the initial stages of cathodic corrosion. The number of nanocrystals increases at more negative potentials due to the greater nucleation density induced by the higher concentration of dissolved Au species. Polarization times above 5.0 min result in fractal growth indicated by the appearance of multi-armed nanostructures. This work not only advances our understanding of the initial stages of nanocrystal formation but also offers a powerful means for controlling the shape and size of metal nanocrystals simply by the rational design of the cathodic corrosion.

Tailoring Cu Electrodes for Enhanced CO2 Electroreduction through Plasma Electrolysis in Non‐Conventional Phosphorus‐Oxoanion‐Based Electrolytes

“…From a structure and symmetry point of view, the octahedral nanocrystals are indicative of a (111)‐surface [43,61] . The anodic peak at around 0.01 V and the cathodic peak at about −0.09 V vs. RHE, related to the adsorption and desorption of OH on Cu(111) terraces, reveal that the anodic polarization in Na 2 H 2 PO 2 generates Cu(111) facets (Figure 4b).…”

“…From a structure and symmetry point of view, the octahedral nanocrystals are indicative of a (111)-surface. [43,61] The anodic peak at around 0.01 V and the cathodic peak at about À 0.09 V vs. RHE, related to the adsorption and desorption of OH on Cu(111) terraces, reveal that the anodic polarization in Na 2 H 2 PO 2 generates Cu(111) facets (Figure 4b). On the other hand, the absence of (111)-features in some of the voltammograms (Figure 4b) might result from the formation of small (111) terraces and the high ratio of step-to-terrace sites.…”

Metal deposition and electrocatalysis for elucidating structural changes of gold electrodes during cathodic corrosion

“…18,[24][25][26][27] It is demonstrated that metal corrosion under cathodic polarization can arise in a range of conditions, from mild (at pH 7 and E = −1 V vs. SHE) to extremely harsh conditions (such as in a 10 M NaOH or KOH electrolyte and E < −5 V vs. SHE). 19,[28][29][30][31][32] For instance, Pt dissolution at moderate negative potentials during ORR in water and organic media was observed. 29,30 In highly-concentrated electrolytes such as 10 M NaOH, the cathodic corrosion of Pt starts already at −1.3 V vs. SHE, resulting in highly anisotropic etching.…”

“…Previously, we demonstrated that the cathodic polarization of polycrystalline Au electrodes in KOH and NaOH alters substantially the crystallographic orientation of surface facets, in which the (111)facets are enriched but to a different extent. 25,31 Furthermore, well-defined octahedral Au nanocrystals and triangular pits are formed by using NaOH and KOH solutions, respectively. 25,31 Here, we examined the electrocatalytic behavior of these nanostructured Au electrodes towards HER and FAOR, aiming to understand the impacts of cathodic corrosion on the surface structure and catalytic activity of metal electrodes.…”

“…SHE). 19,28–32 For instance, Pt dissolution at moderate negative potentials during ORR in water and organic media was observed. 29,30 In highly-concentrated electrolytes such as 10 M NaOH, the cathodic corrosion of Pt starts already at −1.3 V vs .…”