Cathodic corrosion of Au in aqueous methanolic alkali metal hydroxide electrolytes: Notable role of water

Abstract

Cathodic corrosion is an electrochemical process that induces restructuring, roughening, and etching of metal surfaces at a highly negative surface charge density, yet, details of the reaction mechanism are not fully resolved. An in‐depth fundamental understanding of the processes and parameters underlying cathodic corrosion is crucial for tailoring the surface structure of the metal electrodes and for synthesizing shape‐ and size‐controlled nanoparticles. Here, we investigate the relevance of water and hydrogen evolution in the cathodic corrosion process. To achieve this aim, Au electrodes were polarized at ‐1.6 V versus RHE in KOH and NaOH electrolytes prepared using different water + methanol mixtures. Structural changes of the Au surfaces were studied by cyclic voltammetry and monitored by scanning electron microscopy (SEM). Most importantly, cathodic corrosion does not take place in the absence of water. There is no detectable bubble formation due to the hydrogen evolution reaction on Au in purely methanolic alkali. Furthermore, the electrochemically active surface area, facet distribution, and surface morphology of Au electrodes are significantly altered upon cathodic polarization as a function of the water concentration. Cathodic corrosion features become more and more pronounced with a further increase in water content. In addition, substantial differences in the surface structure of Au are observed as a function of the nature and concentration of alkali metal cations. Overall, this study provides a more detailed understanding of the role of water and the hydrogen evolution reaction in dominating cathodic corrosion, which might advance the understanding of this phenomenon.

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

“…Moreover, the current in these voltammetric profiles is normalized to the electrochemically active surface area (EASA). The EASA has been estimated by equating the double‐layer capacity of the anodically polarized and as‐polished Cu electrodes at −0.10 V vs. RHE, where neither Faraday reactions nor adsorption processes occur [30,55–57] . Generally, for Cu electrodes, the peaks observed in the regime between 0.2 V and 0.4 V vs. RHE can be ascribed to the formation and reduction of Cu 2 O [58] .…”

“…The EASA has been estimated by equating the double-layer capacity of the anodically polarized and as-polished Cu electrodes at À 0.10 V vs. RHE, where neither Faraday reactions nor adsorption processes occur. [30,[55][56][57] Generally, for Cu electrodes, the peaks observed in the regime between 0.2 V and 0.4 V vs. RHE can be ascribed to the formation and reduction of Cu 2 O. [58] The peaks at potentials below 0.2 V can be attributed to OH adsorption and desorption on different low-index surface facets.…”

Influence of Residual Water Traces on the Electrochemical Performance of Hydrophobic Ionic Liquids for Magnesium‐Containing Electrolytes

“…[49,50] The presence of water, even at low concentrations, might trigger cathodic corrosion of Au(111) at potentials negative to the hydrogen evolution regime and consequently induces prominent structural changes. [37,51] Thus, we have investigated the electrochemical behavior of Au(111) in MPPip-TFSI and BMP-TFSI at potential regimes, where both the electrolyte and working electrode are stable.…”

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

“…Cathodic corrosion is an electrochemical etching process that restructures and possibly dissolves metal surfaces upon polarization at sufficiently negative potentials in the presence of non-reducible cations. 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.…”

“…), the polarization time, the applied electrode potential, and the electrochemical properties of the metal itself. 16,18,19,26,33 Normally, the restructuring of metal surfaces can have a significant impact on its kinetics, intrinsic activity and selectivity, stability, and reaction mechanisms in (electro) catalysis. 20,25,34,35 Thus, cathodic corrosion can also be beneficially applied to tailor the surface structure of an electrocatalyst, thereby unveiling sites with favorable catalytic properties.…”