Accelerated Photolysis of H2O2 at the Air–Water Interface of a Microdroplet

Photochemical homolysis of hydrogen peroxide (H₂O₂) occurs widely in nature and is a key source of hydroxyl radicals (·OH). The kinetics of H₂O₂ photolysis play a pivotal role in determining the efficiency of ·OH production, which is currently mainly investigated in bulk systems. Here, we report considerably accelerated H₂O₂ photolysis at the air-water interface of microdroplets, with a rate 1.9 × 10³ times faster than that in bulk water. Our simulations show that due to the trans quasiplanar conformational preference of H₂O₂ at the air-water interface compared to the bulk or gas phase, the absorption peak in the spectrum of H₂O₂ is significantly redshifted by 45 nm, corresponding to greater absorbance of photons in the sunlight spectrum and faster photolysis of H₂O₂. This discovery has great potential to solve current problems associated with ·OH-centered heterogeneous photochemical processes in aerosols. For instance, we show that accelerated H₂O₂ photolysis in microdroplets could lead to markedly enhanced oxidation of SO₂ and volatile organic compounds.