# Oxide Growth and Place-Exchange on Au(111) in Alkaline Electrolyte

## TL;DR

This study explores how gold surfaces oxidize in alkaline conditions, revealing slow and irreversible changes that impact electrocatalyst stability.

## Contribution

The paper provides new insights into Au(111) oxidation in alkaline media using electrochemical scanning tunneling microscopy.

## Key findings

- A surface oxide layer grows across Au(111) terraces via a slow place-exchange process.
- Vacancy islands form and persist after place-exchange, preventing surface restoration.
- Oxidation in alkaline media shows kinetically limited dynamics unlike acidic conditions.

## Abstract

Understanding the
oxidation processes of noble metals
is essential
for the elaborate design of functional and stable materials for electrochemical
applications, where electrocatalysis is currently central due to the
need for efficient direct energy conversion devices. Single crystalline
gold (Au(111)) is an important noble metal standard, as it has high
relevance as an electrocatalyst material and is best suited for the
study of fundamental surface and interface processes due to its high
nobility and the model applicability of the processes at its electrified
solid/liquid interface. Under electrochemical conditions, Au(111)
oxidation proceeds via a place-exchange mechanism, in which surface
Au atoms exchange positions with adsorbed oxygen species. While this
process is well studied in acidic media, where it results in the nucleation
and growth of adatom and vacancy islands alongside partial dissolution,
its behavior in alkaline media remains less explored. Here, we investigate
the oxidation of Au(111) in 0.1 M NaOH, providing new insights into
the oxidation process and associated surface restructuring mechanisms.
Using electrochemical scanning tunneling microscopy, we directly observe
the growth of a surface oxide layer across the Au(111) terraces, which
reveals the slow, kinetically limited dynamics of the place-exchange
process. Once this place-exchange process has occurred, the pristine
surface structure is not restored upon electrochemical reduction within
experimental time scales, as vacancy islands form and persist. These
findings are crucial for developing strategies to mitigate catalyst
degradation and enhance the stability of Au-based materials in electrochemical
applications.