Abundant Production of Reactive Water Radical Cations under Ambient Conditions

Abstract

Water radical cations, the crucial intermediates in many aqueous reactions and biochemical processes, are difficult to investigate experimentally due to their short lifetime and low abundance. Herein, a homemade device based on energy-tunable discharge was employed to deposit suitable amounts of energy to atmospheric pressure pure water vapor for abundant production of water radical cations, stabilized as (H2O)n+• (n = 2-5) with a maximal abundance of ≥8.3 × 106 cps for (H2O)2+•, characterized by mass spectrometry (MS). The abundance of water radical cations was optimized by adjusting the experimental parameters such as the discharge voltage (2.5 kV), temperature of the MS inlet (140 °C), carrier gas flow (20 mL/min), and the distance between the discharge tip and MS inlet (12 mm). The ambient formation of water radical cations was further confirmed by the high reactivity of as-prepared water radical cations, which reacted with benzene, ethyl acetate, and dimethyl disulfide instantly, showing rich chemistry with ionic and radical characteristics. Moreover, the computations usingCCSD(T)//MP2 method and density functional theory confirmed that the O-O single-electron bound dimer (B), as well as the hydronium hydroxyl radical complex (A), accounted for the unusual chemistry of the water radical cations, providing a facile approach to access the high reactivity of water radical cations under the ambient conditions.