High CO-Tolerant Ru-Based Catalysts by Constructing an Oxide Blocking Layer.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Carbon monoxide (CO) poisoning severely limits the performance and durability of platinum-group metal catalysts, especially in proton exchange membrane fuel cells during hydrogen oxidation reactions.
• Developing CO-tolerant electrocatalysts is crucial for advancing fuel cell technology and enabling widespread adoption.

Purpose of the Study:

• To design and investigate a novel catalyst with enhanced tolerance to CO poisoning for hydrogen electrooxidation.
• To elucidate the mechanism behind the observed CO tolerance in the new catalyst system.

Main Methods:

• Synthesis of ruthenium oxide-coated ruthenium nanoparticles supported on titanium dioxide (Ru@RuO2/TiO2).
• Electrochemical testing using rotating disk electrode (RDE) to evaluate hydrogen electrooxidation activity and CO tolerance.
• Stability testing in a 1% CO/H2 environment for extended periods.
• Ab initio molecular dynamics (AIMD) simulations to understand CO adsorption and diffusion behavior at the atomic level.

Main Results:

• The Ru@RuO2/TiO2 catalyst exhibited CO tolerance to 1-3% CO, an improvement of approximately two orders of magnitude compared to traditional PtRu/C catalysts.
• The catalyst demonstrated stable operation in 1% CO/H2 for 50 hours, with about 20% of active sites remaining functional even in pure CO.
• AIMD simulations revealed that a hydrous metal oxide shell effectively blocks CO adsorption, rather than promoting CO oxidation, suppressing CO diffusion and adsorption through confined water.

Conclusions:

• The Ru@RuO2/TiO2 catalyst offers a significant advancement in CO tolerance for hydrogen electrooxidation.
• The CO tolerance mechanism is attributed to an oxide blocking layer, not bifunctional activity.
• This oxide blocking layer approach provides a promising strategy for designing next-generation, highly CO-tolerant electrocatalysts for fuel cell applications.