Tuning Ru-O Coordination for Switching Redox Centers in Acidic Oxygen Evolution Electrocatalysis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Achieving high activity and stability in ruthenium dioxide (RuO₂)-based catalysts for the acidic oxygen evolution reaction (OER) requires controlling lattice oxygen involvement (oxygen redox) while promoting metal redox.
• Current strategies often struggle to selectively activate metal redox pathways and suppress undesired oxygen redox.

Purpose of the Study:

• To develop a precise strategy for selectively activating the metal redox process and suppressing the oxygen redox pathway in RuO_x catalysts for acidic OER.
• To enhance catalytic activity and long-term stability by fine-tuning the Ru-O coordination number in amorphous RuO_x.

Main Methods:

• Fabrication of amorphous RuO_x with controlled Ru-O coordination numbers.
• Electrochemical characterization of the oxygen evolution reaction (OER) performance.
• X-ray absorption spectroscopy and operando spectroscopic techniques.
• Theoretical calculations to elucidate reaction mechanisms.

Main Results:

• The optimized amorphous RuO_x catalyst demonstrated outstanding acidic OER performance with a low overpotential of 215 mV at 10 mA cm^-2.
• Exceptional stability was achieved, maintaining performance for 300 hours with a degradation rate of 100 µV h^-1.
• Identification of Ru₂-O₁₁ moieties as key active sites that selectively activate metal redox, suppress lattice oxygen involvement, and lower energy barriers.

Conclusions:

• Fine-tuning the Ru-O coordination number in amorphous RuO_x enables selective activation of metal redox, leading to superior acidic OER performance.
• The Ru₂-O₁₁ moiety plays a critical role in enhancing catalytic activity and stability by controlling redox pathways.
• This strategy provides a new approach for designing advanced electrocatalysts by controlling redox centers and reaction mechanisms.