CeO2 supported high-valence Fe oxide for highly active and stable water oxidation

Abstract

Despite the high intrinsic electrocatalytic activity for the oxygen evolution reaction (OER), stable high valence metal ions such as Fe⁴⁺ are very difficult to form in oxide catalysts. In this work, by elaborating a novel Fe^HV/CeO₂@NF (nickel foam) catalyst, we stabilized high-valence Fe ions on a CeO₂ support and achieved a record low overpotential of 219 mV to reach the current density of 50 mA cm⁻². Theoretical calculations revealed that the fluent d–f electron transfer between ultra-small FeO_x nanoparticles (US-FeO_x) and CeO₂ guarantees the robust high valence of surface Fe sites, which enables the optimum adsorption and efficient conversions in the OER process. Meanwhile, the electronic modulations induced by the US-FeO_x also improve the site-to-site electron transfer to lower the reaction energy barriers for excellent OER performance. Moreover, the Fe^HV/CeO₂@NF catalyst delivered excellent stability, sustaining a high current density (200 mA cm⁻²) for over 500 h, and the simple preparation method gave access to a large-area electrode (100 cm²), paving the way for large-scale hydrogen production by water splitting.