Oxygen-Vacancy-Mediated Dynamic Bidirectional Oxygen Migration for Enhanced Acidic Oxygen Evolution Reaction.
basic_science · Level V
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- Record sourced from PubMed, PMID 42219778.
- Also identified by DOI 10.1021/acsnano.6c01896.
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Abstract
Achieving low iridium (Ir) loading and long-term stability of the membrane electrode assembly remains a major challenge in proton exchange membrane water electrolysis (PEMWE). Here, an Ir-based catalyst supported on titanium oxide (IrO<sub><i>x</i></sub>@E-TiO<sub><i>x</i></sub>) is synthesized through one-step transformation of Ir species anchored on an expanded Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene (E-MXene) template. The uniform dispersion of IrO<sub><i>x</i></sub> enables optimal Ir utilization and the formation of an efficient conductive network, achieving a specific mass activity of 2630 ± 185 A g<sub>Ir</sub><sup>-1</sup> at 1.60 V and 852 ± 62 A g<sub>Ir</sub><sup>-1</sup> at 1.55 V (vs RHE) for the oxygen evolution reaction (OER), with an Ir loading as low as 32.5 wt %. During E-MXene oxidation, oxygen vacancy (O<sub>v</sub>)-rich TiO<sub><i>x</i></sub> forms <i>in situ</i>, promoting a reversible O<sub>v</sub>s-mediated bidirectional oxygen migration process, as evidenced by <i>in situ</i> Raman spectroscopy and theoretical modeling. This dynamic migration fine-tunes the adsorption-desorption energetics of OER intermediates, enhancing both activity and stability under acidic conditions. Moreover, the porous architecture of IrO<sub><i>x</i></sub>@E-TiO<sub><i>x</i></sub> improves mass transport and lowers diffusion resistance in PEMWE, enabling stable operation exceeding 500 h at an Ir loading of 0.33 mg<sub>Ir</sub> cm<sup>-2</sup> with a negligible decay. This study elucidates O<sub>v</sub>s-mediated interfacial dynamics and provides a viable strategy for designing low-Ir, high-performance OER catalysts for practical PEMWEs.