Sulfur-Doped IrO<sub>2</sub> Enable Pathway Switch to Lattice Oxygen Mechanism with Enhanced Stability for Low Iridium PEM Water Electrolysis.
basic_science · Level V
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- Record sourced from PubMed, PMID 40545917.
- Also identified by DOI 10.1002/adma.202507560.
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Abstract
Achieving high activity and stability while minimizing Ir usage poses a significant challenge in the industrialization of proton exchange membrane water electrolysis (PEMWE). Herein we report a sulfur-doping strategy that enables the OER pathway on IrO<sub>2</sub> nanoparticles (IrO<sub>2</sub>/S) to switch from conventional adsorption evolution mechanism (AEM) to lattice oxygen mechanism (LOM) while maintaining Ir─O bond stability, thus achieving a significant enhancement in both intrinsic activity and durability. Advanced spectroscopies and theoretical calculations reveal that the Ir─S coordination motif within the lattice increases the electron density of the Ir center and enhances Ir─O covalency, thus triggering the LOM pathway. Importantly, the lattice distortion and unsaturated Ir─O coordination within the IrO<sub>2</sub>/S generate the oxygen nonbonding state that acts as an electron sacrificial agent to preserve Ir─O bonds upon the LOM-dominated OER process. As a result, PEMWE integrated with such IrO<sub>2</sub>/S electrocatalyst delivers a low cell voltage (1.769 V at 2.0 A cm<sup>-2</sup>) and long-term stability (16.6 µV h⁻¹ over 1000 h@1.0 A cm⁻<sup>2</sup>) while dramatically reducing Ir usage from 1.0 to 0.3 mg cm<sup>-2</sup>. This work establishes S doping as a viable strategy to trigger LOM and stabilize lattice oxygen redox in Ir-based catalysts, opening a new avenue for low-Ir PEMWEs.