Iridium Single-Atom-Ensembles Stabilized on Mn-Substituted Spinel Oxide for Durable Acidic Water Electrolysis.
basic_science · Level V
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- Record sourced from PubMed, PMID 39318088.
- Also identified by DOI 10.1002/adma.202401648.
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Abstract
Exploring single-atom-catalysts for the acidic oxygen evolution reaction (OER) is of paramount importance for cost-effective hydrogen production via acidic water electrolyzers. However, the limited durability of most single-atom-catalysts and Ir/Ru-based oxides under harsh acidic OER conditions, primarily attributed to excessive lattice oxygen participation resulting in metal-leaching and structural collapse, hinders their practical application. Herein, an innovative strategy is developed to fabricate short-range Ir single-atom-ensembles (Ir<sub>SAE</sub>) stabilized on the surface of Mn-substituted spinel Co<sub>3</sub>O<sub>4</sub> (Ir<sub>SAE</sub>-CMO), which exhibits excellent mass activity and significantly improved durability (degradation-rate: ≈2 mV h<sup>-1</sup>), outperforming benchmark IrO<sub>2</sub> (≈44 mV h<sup>-1</sup>) and conventional Ir<sub>single-atoms</sub> on pristine-Co<sub>3</sub>O<sub>4</sub> for acidic OER. First-principle calculations reveal that Mn-substitution in the octahedral sites of Co<sub>3</sub>O<sub>4</sub> substantially reduces the migration energy barrier for Ir<sub>single-atoms</sub> on the CMO surface compared to pristine-Co<sub>3</sub>O<sub>4</sub>, facilitating the migration of Ir<sub>single-atoms</sub> to form strongly correlated Ir<sub>SAE</sub> during pyrolysis. Extensive ex situ characterization, operando X-ray absorption and Raman spectroscopies, pH-dependence activity tests, and theoretical calculations indicate that the rigid Ir<sub>SAE</sub> with appropriate Ir-Ir distance stabilized on the CMO surface effectively suppresses lattice oxygen participation while promoting direct O─O radical coupling, thereby mitigating Ir-dissolution and structural collapse, boosting the stability in an acidic environment.