# Surface Structure Modulation of La0.6Sr0.4CoO3 Films on SrTiO3 (001) Substrate under Electrochemical Conditions

## TL;DR

This study investigates how the surface structure of a water-splitting catalyst changes under electrochemical conditions, affecting its performance.

## Contribution

The paper reveals reversible structural changes in La0.6Sr0.4CoO3 films under electric potential, linking them to catalytic activity.

## Key findings

- Electrochemical treatment adds an edge-shared CoO6 double layer to the surface.
- Polarization in the SrCoO3 region decreases significantly after treatment.
- Structural changes correlate with increased electrode current and catalytic activity.

## Abstract

The surface structure of the La0.6Sr0.4CoO3 film, a typical model water-splitting catalyst, is
examined
under vacuum and electrochemical conditions using surface X-ray diffraction.
The pristine sample has a two-unit-cell-thick strongly polarized SrCoO3 layer at the surface, and the surface termination is predominantly
a CoO2 layer with apical oxygen atoms. After electrochemical
treatment, the surface was covered with an additional edge-shared
CoO6 double layer. The polarization in the SrCoO3 region was greatly reduced. These structural changes were accompanied
by an increase in the working electrode current, suggesting a strong
relationship between surface structure modulation and catalytic activity.
Reversible structural modulation induced by the film’s electric
potential was observed and was qualitatively understood as atomic
displacements caused by the local electric field and change in the
Co ionic radii.