Integrating Interactive Ir Atoms into Titanium Oxide Lattice for Proton Exchange Membrane Electrolysis.

Abstract

Iridium (Ir)-based oxide is the state-of-the-art electrocatalyst for acidic water oxidation, yet it is restricted to a few Ir-O octahedral packing modes with limited structural flexibility. Herein, the geometric structure diversification of Ir is achieved by integrating spatially correlated Ir atoms into the surface lattice of TiO₂ and its booting effect on oxygen evolution reaction (OER) is investigated. Notably, the resultant i-Ir/TiO₂ catalyst exhibits much higher electrocatalytic activity, with an overpotential of 240 mV at 10 mA cm^-2 and excellent stability of 315 h at 100 mA cm^-2 in acidic electrolyte. Both experimental and theoretical findings reveal that flexible Ir─O─Ir coordination with varied geometric structure plays a crucial role in enhancing OER activity, which optimize the intermediate adsorption by adjusting the d-band center of active Ir sites. Operando characterizations demonstrate that the interactive Ir─O─Ir units can suppress over-oxidation of Ir, effectively widening the stable region of Ir species during the catalytic process. The proton exchange membrane (PEM) electrolyzer, equipped with i-Ir/TiO₂ as an anode, gives a low driving voltage of 1.63 V at 2 A cm^-2 and maintains stable performance for over 440 h. This work presents a general strategy to eliminate the inherent geometric limitations of IrO_x species, thereby inspiring further development of advanced catalyst designs.