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 IrOx species, thereby inspiring further development of advanced catalyst designs.