# Bulk and Surface Dual‐Modification for Stabilizing RuO2 Anode in 2 A cm−2 PEMWE Operation

## TL;DR

A new strategy combining bulk and surface modifications improves the stability of RuO2 anodes for efficient water splitting at high current densities.

## Contribution

A dual-modification approach using Cr doping and Si surface treatment enhances both activity and durability of RuO2 anodes in PEMWEs.

## Key findings

- Cr doping suppresses Ru overoxidation and promotes charge transfer in the bulk phase.
- Si surface modification inhibits catalyst reconstruction and protects the Cr dopant.
- The modified RuO2 anode achieves stable operation at 2 A cm−2 and 1.65 V in PEMWE.

## Abstract

RuO2 is a promising alternative to IrO2 for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWEs). However, to date, only Ir oxide or IrRu‐oxide based anodes have demonstrated possible stable operation at industrial‐relevant current densities of 2 A cm−2 for practical PEMWE applications. The poor durability of Ir‐free RuO2 anodes remains a major barrier to its practical use. While metal doping has been extensively explored to stabilize the Ru valence, emerging evidence suggests a multifactorial failure mechanism involving both physical and chemical degradation of RuO2 anodes. This underscores the need for strategies that stabilize both the catalyst bulk structure and reaction interface in OER. Here, we report a dual‐modification strategy combining bulk Cr substitution with Si surface modification to simultaneously enhance the intrinsic activity and stability of RuO2‐based anode in PEMWE. Cr doping modulates the Ru valence state in the bulk phase, promoting charge transfer while suppressing Ru overoxidation, whereas Si modification stabilizes the reaction interface by inhibiting catalyst reconstruction and protecting the Cr dopant. The resulting catalyst achieves stable operation in PEMWE at 2 A cm−2 and 1.65 V. This work provides new insights into the development of RuO2‐based catalysts and electrodes for PEMWEs.

The high‐current‐density stability of the RuO2‐based anode in PEMWE could be taken care of by a bulk and surface dual modification strategy developed in this work, where Cr doping modulates the Ru valence state in the bulk phase, suppressing Ru overoxidation, whereas Si modification stabilizes the reaction interface by inhibiting catalyst reconstruction and protecting the Cr dopant.