Iridium oxide nanoribbons with metastable monoclinic phase for highly efficient electrocatalytic oxygen evolution

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Metastable metal oxides with ribbon morphologies show potential for energy conversion catalysis.
• Current synthesis methods for these materials are limited.
• Iridium oxide (IrO2) is a key catalyst, but its structural control is challenging.

Purpose of the Study:

• To develop a novel synthesis method for metastable metal oxides with ribbon morphologies.
• To synthesize and characterize monoclinic phase iridium oxide nanoribbons.
• To evaluate the electrocatalytic performance of the synthesized nanoribbons for the oxygen evolution reaction.

Main Methods:

• Molten-alkali mechanochemical synthesis.
• Conversion of a monoclinic K0.25IrO2 precursor.
• Characterization using X-ray diffraction and electron microscopy.
• Density functional theory (DFT) calculations.
• Electrochemical testing for oxygen evolution reaction (OER) in acidic media.

Main Results:

• Successful synthesis of monoclinic phase iridium oxide nanoribbons (space group C2/m).
• Demonstration of a novel molten-alkali mechanochemical route for nanoribbon formation.
• Identification of a lower d band center in monoclinic IrO2 compared to tetragonal IrO2 via DFT.
• Monoclinic IrO2 nanoribbons showed higher intrinsic catalytic activity for OER than tetragonal IrO2.

Conclusions:

• A new molten-alkali mechanochemical method enables the synthesis of monoclinic IrO2 nanoribbons.
• The unique monoclinic structure of IrO2 nanoribbons enhances their electrocatalytic activity for OER.
• This work offers a promising strategy for designing advanced catalysts for energy conversion applications.