Non-leaching cerium oxide evolved from Laves phase enables iron-retentive oxygen evolution

Iron-based compounds transform in situ into iron (oxyhydr)oxides (FeO x H y ) during the alkaline oxygen evolution reaction (OER), serving as active species but suffering from aggregation, poor conductivity, and Fe leaching. To address these limitations, we employ the heterobimetallic rare-earth transition-metal-based Laves-phase CeFe 2 as an OER precatalyst. The robust chemical bonding, ordered atomic arrangement, and inherent oxophilic nature of Ce in the structure drive in situ surface reconstruction of fully oxidized CeFe 2 to a heterostructure composed of α-FeOOH nanodomains uniformly confined within CeO 2 . Comprehensive analyses, including quasi- in situ Raman and X-ray absorption spectroscopy, scanning transmission electron microscopy, and theoretical calculations, confirm that non-leaching CeO 2 prevents Fe dissolution, suppresses α-FeOOH aggregation, and optimizes its electronic structure and rate-determining step. Moreover, the remaining bulk CeFe 2 phase improves charge transfer, collectively enabling the CeFe 2 -based system to significantly outperform directly synthesized FeO x H y references and rival the benchmark NiFeO x H y in OER.