New insight into dispersion stability of IrOx catalyst slurry for polymer electrolyte membrane water electrolysis through real-time comprehensive multiwavelength optical analysis

초록

Polymer electrolyte membrane water electrolysis (PEMWE) has gained international attention as the most promising technology for green hydrogen production. Especially, dispersion stability of catalyst slurry is critical for achieving the high-performance catalyst layer for PEMWE. However, a full understanding of complex aggregation phenomena within the catalyst slurry remains challenging. Herein, we report the first successful attempt to reveal the real-time correlation between flocculation and sedimentation behaviors in IrOx catalyst slurry through comparative wavelength-dependent analysis of dispersion stability. To provide new insight on this relationship, a rapid and nondestructive multiwavelength optical quantification methodology based on the broad visible and near-IR spectral range is devised. It is revealed that the visible stability index (VSI) of IrOx A slurry (42.5 at 550 nm) is 1.2 times higher than that of IrOx B (34.6), and the near-IR stability index (NSI) of IrOx A (25.7 at 880 nm) was 1.6 times higher than that of IrOx B (16.4), suggesting that the dispersion stability of IrOx B slurry is superior to that of IrOx A slurry. Furthermore, the adsorption and flocculation behavior between ionomers and IrOx particles is readily explained through the increasing trend of the VSI values at 450, 550, and 650 nm in the visible region, and sedimentation behavior of large particle aggregates is effectively verified by comparing the NSI values at 880, 1280, and 1640 nm in the near-IR region. Our evaluation methodology can proactively prevent potential problems of the catalyst slurries during electrode process, thereby improving the cell performance of PEMWE.

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