Electride-Stabilized Iridium Nanoparticles with Subsurface Oxygen Confinement for Oxygen Evolution Electrocatalysis

Electrides, with their unique electron-rich architectures, hold transformative potential for catalysis but face critical challenges in electrochemical systems due to inherent instability and synthesis limitations. Here, we present a kinetically controlled gas-solid reaction to synthesize phase-pure Ti₃O electride nanoparticles, which exhibit high electrical conductivity (617 S cm^-1) and broad electrochemical stability window (-0.4 to 2.1 V vs RHE) in acidic media. When used as a support for iridium (Ir) nanocatalysts in the oxygen evolution reaction (OER), the Ti₃O electride demonstrates strong metal-support interactions. These interactions suppress both amorphization and coalescence of the Ir nanoparticles during the OER. Furthermore, Ti₃O promotes oxygen diffusion into the Ir lattice, leading to the formation of subsurface oxygen-confined Ir nanoparticles, a previously unobserved catalytic active phase. This unique configuration shifts the OER mechanism entirely to the adsorbate evolution mechanism (AEM), avoiding participation of the lattice oxygen mechanism (LOM). Consequently, the Ir/Ti₃O catalyst exhibits superior activity and stability compared to pristine Ir nanoparticles or Ir nanoparticles supported on other nonelectride titanium oxides, across both three-electrode cells and proton exchange membrane water electrolyzers. This work establishes electrides as versatile mediators for electronic structure engineering in electrocatalysis, enabling the stabilization of catalytic phases unattainable with conventional supports.