Phase Engineering of Iridium Oxides Enables Direct Coupling of Proton Exchange Membrane Water Electrolysis With Intermittent Electrical Energy.
basic_science · Level V
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- Record sourced from PubMed, PMID 42458888.
- Also identified by DOI 10.1002/adma.74144.
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Abstract
Proton exchange membrane water electrolysis (PEMWE) coupled with intermittent renewables is a leading technology for green hydrogen production, but its large-scale deployment is impeded by the sluggish kinetics and high iridium cost of the anodic oxygen evolution reaction (OER). Crystal phase regulation offers a rational approach to enhance catalyst intrinsic activity, yet a clear phase-activity correlation for IrO<sub>2</sub> under realistic PEMWE conditions remains lacking. Here, we synthesize four crystalline phases of iridium oxide (metastable 1T-, 3R-, Tri-, and conventional Rutile-IrO<sub>2</sub>) and demonstrate a strict phase-dependent OER activity trend: 1T-IrO<sub>2</sub> > 3R-IrO<sub>2</sub> > Tri-IrO<sub>2</sub> > Rutile-IrO<sub>2</sub>. The 1T-IrO<sub>2</sub> catalyst achieves a PEMWE performance of 3 A cm<sup>-2</sup> at only 1.75 V with an Ir loading of 0.4 mg<sub>Ir</sub> cm<sup>-2</sup>, exceeding the U.S. DOE 2026 target. It also shows stable operation for 2000 h at 2 A cm<sup>-2</sup> and maintains durability during 1000 h of dynamic current cycling. In situ XANES/EXAFS analyses link the enhanced activity to a higher Ir oxidation state, while in situ Raman spectroscopy identifies the reaction pathway through characteristic Ir-*OH, Ir-*O, and Ir-*OOH intermediates. This work establishes a direct phase-activity relationship for IrO<sub>2</sub> catalysts and highlights the promise of phase engineering for efficient energy conversion.