Anisotropic etching of platinum electrodes at the onset of cathodic corrosion.

Thomas J P Hersbach,Marc T M Koper,Alexei I Yanson

doi:10.1038/ncomms12653

Abstract

Cathodic corrosion is a process that etches metal electrodes under cathodic polarization. This process is presumed to occur through anionic metallic reaction intermediates, but the exact nature of these intermediates and the onset potential of their formation is unknown. Here we determine the onset potential of cathodic corrosion on platinum electrodes. Electrodes are characterized electrochemically before and after cathodic polarization in 10 M sodium hydroxide, revealing that changes in the electrode surface start at an electrode potential of −1.3 V versus the normal hydrogen electrode. The value of this onset potential rules out previous hypotheses regarding the nature of cathodic corrosion. Scanning electron microscopy shows the formation of well-defined etch pits with a specific orientation, which match the voltammetric data and indicate a remarkable anisotropy in the cathodic etching process, favouring the creation of (100) sites. Such anisotropy is hypothesized to be due to surface charge-induced adsorption of electrolyte cations.

Highlights

Cathodic corrosion is a process that etches metal electrodes under cathodic polarization
These findings of anisotropic etching are supported by scanning electron microscopy (SEM), which reveals the formation of well-oriented etch pits
The electrodes were characterized by cyclic voltammetry (CV) in the hydrogen adsorption/desorption region to determine whether the electrode surface had changed

Summary

Introduction

Cathodic corrosion is a process that etches metal electrodes under cathodic polarization. Electrodes are characterized electrochemically before and after cathodic polarization in 10 M sodium hydroxide, revealing that changes in the electrode surface start at an electrode potential of À 1.3 V versus the normal hydrogen electrode The value of this onset potential rules out previous hypotheses regarding the nature of cathodic corrosion. Besides leading to extensive roughening of the surface, cathodic corrosion generates nanoparticles as a corrosion by-product at strong cathodic polarization, which can be enhanced by introducing an alternating potential These observations have led researchers to hypothesize incorporation and subsequent leaching of electrolyte protons or alkali metals as an explanation for cathodic corrosion[1,2,3]. The strategy employed in this work seems suitable for studying cathodic corrosion on other metals

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Conclusion