Cerium Dioxide as an Electron Buffer to Stabilize Iridium for Efficient Water Electrolysis

Sustaining the steady state for highly active non-stoichiometric iridium (Ir)-based oxide (IrOx) at low Ir loading remains challenging primarily due to the continuous oxidation and sequent dissolution of Ir active sites during the oxygen evolution reaction (OER). In this context, a new iridium-cerium (Ce) substitution solid solution oxide (SSO) has been developed, featuring uniformly dispersed Ir atoms within Ce dioxide (CeO2) matrix as electron buffer, which delivers remarkable acidic OER catalytic activity and enhanced stability. The electron-buffering capacity of CeO2 facilitates the charge transfer toward Ir atoms, leading to abundant active low-valence Ir sites and effectively prevent their oxidation and dissolution. As a result, IrCe SSO demonstrates an overpotential of merely 238 mV@10 mA cm-2. Proton exchange membrane water electrolyzer employing IrCe SSO at a low Ir loading of 396 mu gIr cm-2 operates consistently for over 100 h@500 mA cm-2. Density functional theory (DFT) calculations corroborate that the electron-buffering effect of CeO2 enriches the density of IrIII and substantially increases the dissolution energy barrier of Ir atoms. This study presents a viable approach to addressing the issues of instability and low efficiency in Ir-based OER electrocatalysts for acidic water electrolysis. This work presents an iridium-cerium substitution solid solution oxide catalyst, featuring uniformly dispersed Ir atoms within Ce dioxide matrix as an electron buffer, which achieve impressively enhanced acidic OER activity and durability. The electron-buffering capacity of CeO2 facilitates the charge transfer toward Ir atoms, which generate and stabilize low-valence Ir active sites. image