Mn_0.75Ru_0.25O₂ with Low Ru Concentration for Active and Durable Acidic Oxygen Evolution

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Ruthenium is a potential alternative to iridium for water-splitting anodes but suffers from overoxidation and dissolution.
• Developing stable and active electrocatalysts is crucial for efficient oxygen evolution reaction (OER) in industrial applications.

Purpose of the Study:

• To enhance the activity and stability of electrocatalysts for the oxygen evolution reaction.
• To synthesize an isostructural rutile MnRu oxide with low Ru concentration and develop an asymmetric Mn-O-Ru dual-site active center.

Main Methods:

• Synthesis of isostructural rutile Mn_0.75Ru_0.25O₂.
• Electrochemical testing at industry-relevant conditions.
• Structural analysis and isotopic labeling.

Main Results:

• The synthesized Mn_0.75Ru_0.25O₂ exhibits a low overpotential (154 mV at 10 mA cm^-2) and remarkable stability (670 h at 200 mA cm^-2 with 29 µV/h^-1 degradation).
• A proton exchange membrane water electrolyzer using this catalyst achieved stable operation at 1 A cm^-2 for 700 h (53 µV h^-1 degradation).
• Structural analysis confirmed an asymmetric Mn-O-Ru dual-site active center facilitating the OER via a radical coupling pathway.

Conclusions:

• The asymmetric Mn-O-Ru dual-site active center in isostructural rutile Mn_0.75Ru_0.25O₂ stabilizes cations and lattice oxygen.
• This stabilization enhances both the activity and durability of the electrocatalyst for the oxygen evolution reaction.
• The findings present a promising strategy for developing advanced electrocatalysts for efficient water splitting and hydrogen production.