# Role of Hydration in Uncovering the OER Activity of Amorphous Iridium Oxide Electrocatalysts

## TL;DR

This study shows how hydration affects the performance and stability of iridium oxide catalysts used in oxygen production reactions.

## Contribution

The study reveals hydration's critical role in modulating activity and stability of iridium oxide electrocatalysts.

## Key findings

- Hydrated iridium oxide shows high OER activity but poor stability.
- Crystalline IrO2 has poor activity as its performance is surface-confined.
- Structural changes in commercial iridium oxide are reversible under OER conditions.

## Abstract

Understanding the structural properties of iridium oxide
electrocatalysts
under operational conditions is critical for elucidating the structure–property
relationships that enhance the catalytic activity for the oxygen evolution
reaction. In this study, in situ X-ray absorption
spectroscopy under realistic conditions was employed to investigate
the potentiodynamic and time-resolved structural evolution of a commercial
iridium oxide, alongside its fully hydrated and crystalline counterparts.
Our findings reveal two distinct electrochemical regimes, a low potential
plateau associated with a nonconductive Ir3+ state and
a linear region where small potential variations induce reversible
oxidation state and structural transformations. The structural changes
were found to occur reversibly on the commercial material even after
prolonged exposure to OER potentials. Notably, the hydrated IrO
x
exhibits extremely high OER activity, surpassing
the commercial material by nearly an order of magnitude, yet it suffers
from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears
to be confined to the surface. These findings highlight the critical
role of hydration in modulating both activity and stability, offering
valuable insights for the rational design of next generation iridium
based OER catalysts.