Electronic Backflow Through Oxygen Bridge in RuO_x-Graphdiyne for Stable Acidic Water Oxidation

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing cost-effective and stable catalysts for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWE) is crucial.
• Ruthenium dioxide (RuO₂) is a promising alternative to iridium oxide (IrO_x) but suffers from over-oxidation, limiting its large-scale application.

Purpose of the Study:

• To develop a stable and cost-effective catalyst for OER in PEMWE.
• To investigate the mechanism of preventing over-oxidation of RuO_x species.

Main Methods:

• In situ growth of RuO_x species on graphdiyne (GDY).
• In situ X-ray absorption spectroscopy (XAS) at Ru K-edge and C K-edge to study electronic structure and interactions.
• Performance testing in proton exchange membrane water electrolyzers (PEMWE).

Main Results:

• Formation of a strong electronic metal-support interaction with a Ru─O─C oxygen bridge structure.
• Observation of an unexpected electronic backflow from GDY to RuO_x through the oxygen bridge, stabilizing Ru in a low chemical state and preventing over-oxidation.
• RuO_x-GDY catalyst exhibited a low overpotential (193 mV at 10 mA cm^-2) and remarkable stability (>300 h).
• Achieved a lower cell voltage (1.72 V at 1 A cm^-2) in PEMWE compared to conventional RuO₂ (1.91 V).

Conclusions:

• The in situ grown RuO_x-GDY catalyst effectively prevents Ru over-oxidation via an electronic backflow mechanism.
• This novel catalyst demonstrates superior performance and stability for OER in PEMWE, offering a promising alternative to existing materials.