Activating Lattice Oxygen Mechanism in IrO _<i>x</i> @WO ₃ Composite Electrocatalyst for Enhanced Oxygen Evolution Performance

Proton exchange membrane water electrolysis (PEMWE) holds great promise for green hydrogen production but is limited by sluggish oxygen evolution reaction (OER) kinetics and the high cost of Ir-based electrocatalysts. Herein, a defect-engineered interfacial strategy is proposed to construct atomically thin WO3 nanosheets decorated with IrOx nanoparticles (IrOx@WO3), synthesized via an ultrasonic-assisted exfoliation and high-temperature thermal treatment approach. Comprehensive characterization demonstrated the formation of strong IrOx-WO3 electronic coupling and controllable oxygen vacancy (Ov) defects at the heterointerface, enabling an optimized charge distribution and reliable chemical bonding. Performance studies demonstrated that the synthesized material exhibits excellent OER activity with good mass activity (MA, 0.396 A mgIr–1), outstanding turnover frequency (TOF, 0.244 s–1), exceptional long-term durability (636 h), and remarkable cost-effectiveness (raw material cost only ∼3.8% of commercial IrO2). Unlike previously reported IrOx-WO3 systems, this work highlights the critical role of WO3 nanosheets and interface defect modulation in simultaneously enhancing Ir utilization, OER mechanism regulation, and acid stability. Mechanistic investigations indicated that the optimized low-dimensional morphology, Ov defects, and interfacial electron modulation not only collectively induced the activation of the lattice oxygen mechanism (LOM), but also effectively suppressed the formation of peroxo species and lattice dissolution. As a result, OER kinetics and overall stability were significantly enhanced. Density functional theory (DFT) calculations further confirmed that interface engineering effectively optimized the d-band center (εd = −3.78 eV) and reduced the adsorption barriers of intermediates (ΔGOH*: 1.60 eV). This work provides a mechanistically grounded and scalable strategy for designing efficient, stable, and cost-effective catalysts for advanced energy-conversion systems.