Vanadium-Induced Lattice Compression and Electronic Modulation in Iridium-Ruthenium Electrocatalysts Boost Acidic...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient and stable electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing proton-exchange-membrane water electrolyzers (PEMWEs).
• Current Ir-Ru alloy catalysts often rely on less efficient OER mechanisms, limiting PEMWE performance.
• A need exists for novel catalyst designs that promote faster reaction kinetics and enhance long-term stability in acidic media.

Purpose of the Study:

• To investigate the effect of vanadium incorporation into Ir-Ru alloys on OER electrocatalytic activity and mechanism.
• To explore a new catalytic pathway for OER using a ternary Ir-Ru-V electrocatalyst.
• To provide a design strategy for high-performance, low-iridium OER catalysts.

Main Methods:

• Synthesis and characterization of Ir₂₇Ru₂₀V₅₃ electrocatalyst using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM).
• Mechanistic studies employing kinetic isotope effect (KIE) and kinetic probe experiments with methanol and tetramethylammonium.
• Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to identify reaction intermediates.
• Electrochemical testing in a PEMWE setup to evaluate activity and durability.

Main Results:

• The Ir₂₇Ru₂₀V₅₃ catalyst demonstrated lattice compression and shortened metal-metal bonds, influencing electronic structure.
• Evidence strongly suggests a direct O-O coupling pathway, distinct from conventional mechanisms (LOM, AEM), was operative.
• Operando ATR-SEIRAS confirmed the presence of O-O intermediates, supporting the proposed direct coupling mechanism.
• The catalyst achieved a low overpotential of 213 mV at 10 mA cm^-2 and exceptional durability (70 μV h^-1 degradation over 570 h at 100 mA cm^-2) in a PEMWE.

Conclusions:

• Incorporating vanadium into Ir-Ru alloys fundamentally alters the OER catalytic mechanism towards a more efficient direct O-O coupling pathway.
• The Ir₂₇Ru₂₀V₅₃ electrocatalyst offers a promising high-performance and durable alternative for PEMWEs, reducing reliance on iridium.
• This study presents a viable strategy for designing advanced OER catalysts by controlling reaction mechanisms through early transition metal incorporation.