Surface sulfonic-group bonded oxygen evolution catalyst for proton exchange membrane water electrolysis

Area of Science:

• Electrochemistry
• Materials Science

Background:

• Proton transport is vital for the oxygen evolution reaction (OER).
• Iridium oxide (IrO_x) is stable but lacks activity at high current densities.
• Sulfonates improve proton transfer but suffer from leaching, compromising stability.

Purpose of the Study:

• To develop a stable, highly active electrocatalyst for the oxygen evolution reaction.
• To investigate the effect of covalently bonded sulfonic acid groups on catalyst performance.
• To address the leaching issue associated with traditional sulfonate incorporation.

Main Methods:

• Synthesized a sulfonic acid (SO₃H) grafted catalyst, Ir/IrO_x~SO₃H, with covalent bonding.
• Tested the catalyst in a proton exchange membrane water electrolysis (PEMWE) cell.
• Evaluated catalyst stability and activity at high current density (3.0 A cm^-2).

Main Results:

• Ir/IrO_x~SO₃H achieved a cell voltage of 1.75 V at 3.0 A cm^-2, outperforming commercial IrO_x.
• The catalyst operated stably for over 1000 hours without sulfonate leaching.
• Covalent bonding enhanced proton transfer and promoted *OOH intermediate formation, accelerating OER kinetics.
• Elevated surface potential reduced particle agglomeration, aiding membrane electrode assembly.

Conclusions:

• Covalently bonded sulfonic acid groups significantly enhance OER activity and stability.
• The developed Ir/IrO_x~SO₃H catalyst is a promising candidate for energy conversion.
• This strong bonding strategy offers a pathway for advanced sulfonate-grafted electrocatalysts.