Distance Effect Induces Short-Range Electronic State Coupling in Ir Dual Atom Catalysts for Acidic Water Oxidation

Accurately controlling the spacing between active sites plays a key role in enhancing activity and lowering the cost for the acidic oxygen evolution reaction (OER). Here, Ir atomically dispersed catalysts with different single atom distances, including the Ir single atom catalyst, Ir dual atom catalyst (DAC), and Ir triple atom catalyst, are prepared by using a deposition-precipitation approach. Remarkably, Ir DAC with atomic spacing of 2.6 Å only needs 210 mV at 10 mA cm^-2 and the corresponding mass activity is 51.7 times of commercial IrO₂ during OER. In situ Raman spectroscopy and theoretical calculations illustrate the distance effect induces the short-range electronic state coupling between intersite Ir atoms, which optimizes the adsorption strength of the active *O_x(OH)_y in Ir DAC, and thus boosts acidic OER kinetics. Finally, the Ir DAC assembled in proton exchange membrane water electrolysis shows over 1200 h durability under the industrial current density of 1000 mA cm^-2. The economic accounting of the Pt/C||Ir DAC device is US$ 0.95 per kg H₂, which is lower than the 2030 DOE target of US$ 1.0 per kg of H₂.