Regulating Metal–Support Interaction via WO ₃ Crystal Phase Engineering for Enhanced Acidic Water Oxidation

ABSTRACT

Metal–support interaction (MSI) is pivotal in tuning the intrinsic activity and structural stability of heterogeneous catalysts, yet precise control of MSI strength remains a major challenge. Herein, we demonstrate crystal‐phase engineering of WO ₃ supports—monoclinic (M‐WO ₃ ), orthorhombic (O‐WO ₃ ), and tetragonal (T‐WO ₃ )—to modulate MSI in Ir single‐atom catalysts. The three WO ₃ crystals exhibit distinct distortion degrees (M‐WO ₃ > O‐WO ₃ > T‐WO ₃ ), where stronger distortion enhances Ir activity but compromises stability. Notably, O‐WO ₃ achieves an optimal modulation balance: the moderate W─O bond strength and distortion induce the strongest MSI, elevating the Ir oxidation state to +5.74, shortening the Ir─O bond, and reinforcing Ir─O covalency. Such favorable electronic and structural modulation substantially promotes intrinsic oxygen evolution reaction (OER) activity. The O─WO ₃ ─Ir catalyst exhibits a low overpotential of 219 mV at 10 mA cm ⁻² and demonstrates outstanding acidic OER stability, with a cumulative operation time over 1000 h under sequential testing at different current densities. The optimized MSI promotes high‐valence Ir formation, accelerates *OO intermediate generation, and suppresses Ir dissolution, thereby addressing sluggish kinetics and unstable active sites. This work provides new insights into regulating MSI strength via crystal‐phase engineering to advance durable and efficient acidic OER catalysts.