Photochemical synthesis of H2O2 from the H2O•••O(3P) van der Waals complex:: Experimental observations in solid krypton and theoretical modeling

Productive photochemical synthesis of hydrogen peroxide, H2O2, from the H2O center dot center dot center dot O(P-3) van der Waals complex is studied in solid krypton. Experimentally, we achieve the three-step formation of H2O2 from H2O and N2O precursors frozen in solid krypton. First, 193 nm photolysis of N2O yields oxygen atoms in solid krypton. Upon annealing at similar to 25 K, mobile oxygen atoms react with water forming the H2O center dot center dot center dot O complex, where the oxygen atom is in the triplet ground state. Finally, the H2O center dot center dot center dot O complex is converted to H2O2 by irradiation at 300 nm. According to the complete active space self-consistent field modeling, hydrogen peroxide can be formed through the photoexcited H2O+-O- charge-transfer state of the H2O center dot center dot center dot O complex, which agrees with the experimental evidence.