Strain Regulation to Optimize the Acidic Water Oxidation Performance of Atomic‐Layer IrOx

Strain regulation has become an important strategy to tune the surface chemistry and optimize the catalytic performance of nanocatalysts. Herein, the construction of atomic‐layer IrOx on IrCo nanodendrites with tunable IrO bond length by compressive strain effect for oxygen evolution reaction (OER) in acidic environment is demonstrated. Evidenced from in situ extended X‐ray absorption fine structure, it is shown that the compressive strain of the IrOx layer on the IrCo nanodendrites decreases gradually from 2.51% to the unstrained state with atomic layer growth (from ≈2 to ≈9 atomic layers of IrOx), resulting in the variation of the IrO bond length from shortened 1.94 Å to normal 1.99 Å. The ≈3 atomic‐layer IrOx on IrCo nanodendrites with an IrO bond length of 1.96 Å (1.51% strain) exhibits the optimal OER activity compared to the higher‐strained (2.51%, ≈2 atomic‐layer IrOx) and unstrained (>6 atomic‐layer IrOx) counterparts, with an overpotential of only 247 mV to achieve a current density of 10 mA cm−2. Density functional theory calculations reveal that the precisely tuned compressive strain effect balances the adsorbate–substrate interaction and facilitates the rate‐determining step to form HOO*, thus assuring the best performance of the three atomic‐layer IrOx for OER.