Tuning and Shielding Iridium Active Sites Through Tungsten Electron Buffer for Oxygen Evolution Catalysis.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Proton-exchange-membrane water electrolysis (PEMWE) requires efficient and durable oxygen evolution reaction (OER) electrocatalysts for acidic conditions.
• Iridium-based catalysts face challenges due to activity-stability trade-offs, including over-oxidation and corrosion.

Purpose of the Study:

• To develop a novel electrocatalyst that enhances OER activity and stability under acidic conditions for PEMWE.
• To investigate the role of tungsten single atoms in modifying iridium oxide nanoclusters for improved catalytic performance.

Main Methods:

• Synthesis of W single atoms decorated IrO_x nanoclusters on N-doped graphene (W-IrO_x/NG) via solvothermal reaction and NH₃-assisted pyrolysis.
• Characterization of W SAs in W-N₃O₁ configuration linked to IrO_x via W─O─Ir interfaces.
• Electrochemical testing in a PEM electrolyzer and theoretical calculations (DFT) to understand reaction mechanisms.

Main Results:

• W-IrO_x/NG exhibited an ultrahigh mass activity of 2998.91 A g_Ir ^-1 at 300 mV overpotential.
• The catalyst maintained stable operation for over 250 h at 1 A cm^-2 with ultralow Ir loading (0.25 mg_Ir cm^-2).
• Mechanistic studies revealed W atoms act as electron buffers, regulating Ir oxidation states and suppressing over-oxidation.

Conclusions:

• W single atoms integrated with IrO_x nanoclusters significantly enhance OER performance and durability.
• The W-N₃O₁ sites modulate Ir's electronic structure, accelerating OER kinetics by optimizing intermediate binding and deprotonation.
• This W-IrO_x/NG catalyst presents a promising alternative for efficient and stable PEMWE applications.