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

Proton transport plays a crucial role in acidic oxygen evolution reaction process. Iridium oxide (IrO_x) exhibits good stability, yet its catalytic activity remains insufficient at high current density. Trace sulfonates introduced into electrocatalysts can enhance the proton transfer process; however, their significant leaching compromises catalyst stability. Herein, we report a sulfonic groups ( - SO₃H) grafted catalyst, Ir/IrO_x ~ SO₃H, featuring covalent bonding between sulfonic groups and iridium oxide. The anchored sulfonic groups facilitate enhancing the proton transfer process and promote the formation of *OOH intermediates, thereby accelerating the oxygen evolution reaction kinetics. A proton exchange membrane water electrolysis assembled with an Ir/IrO_x ~ SO₃H anode needs a cell voltage of only 1.75 V at 3.0 A cm^-2 and stably operates over 1000 h without leaching of sulfonic groups, outperforming a water electrolysis assembled with a commercial iridium oxide anode in activity. Moreover, the elevated surface potential of catalyst particles alleviates their agglomeration, which is benefit to the industrial membrane electrode preparation. The strong bonding strategy holds promise for advancing the development of sulfonates-grafted catalysts in energy conversion applications.