Dynamic Structural Self-Optimization in Mn and Ta Codoped RuO₂ for Efficient and Long-Term Acidic Water Oxidation.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Ruthenium-based catalysts are crucial for acidic oxygen evolution reactions (OER).
• Catalyst instability, particularly of ruthenium, hinders practical application in OER.
• Understanding dynamic self-optimization is key to developing stable and active catalysts.

Purpose of the Study:

• To investigate the self-optimization process of oxygen species in Mn and Ta codoped RuO2 (MTRO) catalysts.
• To elucidate the role of oxygen diffusion in catalyst stabilization and activity during acidic OER.
• To establish a model for designing robust RuO2-based OER catalysts.

Main Methods:

• Utilized tetramethylammonium cation (TMA+) chemical probes to track deprotonated surface oxygen species.
• Employed differential electrochemical mass spectrometry (DEMS) to analyze oxygen behavior.
• Quantified oxygen diffusion coefficients (DO) and correlated them with catalyst structure and performance.

Main Results:

• Identified a shift in reaction mechanism from lattice oxygen mechanism (LOM) to adsorbate evolution mechanism (AEM).
• Demonstrated that moderate oxygen diffusion drives catalyst reconstruction, leading to a stable, low-coordination structure.
• Achieved a significantly reduced oxygen diffusion coefficient in MTRO (1.40 × 10^-15 cm2 s^-1) compared to undoped RuO2 and MRO.

Conclusions:

• The optimized MTRO catalyst exhibits excellent performance: low overpotential (215 mV at 10 mA cm-2) and remarkable stability (>1200 h in H2SO4, >600 h in PEM electrolyzer).
• Defective, low-coordination structures with moderate oxygen diffusion are crucial for highly active and durable RuO2-based OER catalysts.
• In situ self-optimization modulates catalytic pathways and stabilizes active sites, offering a new paradigm for catalyst design.