Single-Atom Iridium Orchestrates a Reaction Pathway Shift to Activate Lattice Oxygen for Efficient Oxygen Evolution

Abstract

Overcoming the intrinsic limitations of the oxygen evolution reaction (OER) remains a formidable challenge in the pursuit of efficient water splitting. Herein, we demonstrate a method for selective anchoring of an iridium atom near a NiFe layered double hydroxide iron site. This strategy enables the direct formation of the O–O coupling pathway via the lattice oxygen mechanism (LOM), thus circumventing the thermodynamic constraints imposed by the conventional adsorbate evolution mechanism (AEM). The catalyst achieves an ultralow overpotential of 213 mV at 50 mA cm^–2 and maintains 1000 h of operation at 100 mA cm^–2 in alkaline media. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), in situ electrochemical Raman spectroscopy, TMA⁺ cation probing, and pH-dependent analysis collectively provide compelling evidence for the lattice oxygen mechanism (LOM) pathway. When integrated into an anion exchange membrane water electrolyzer (AEMWE), the system delivers 1 A cm^–2 at <1.73 V. Furthermore, density functional theory (DFT) calculations and X-ray absorption fine structure analysis (XAFS) demonstrate that the Ir single atoms enhance metal–oxygen hybridization and raise the O 2p band center, thus promoting the electronic transition from AEM to LOM. These findings not only advance our understanding of single-atom-modulated catalysts but also highlight their potential in optimizing OER systems for energy applications.