Water-solid contact electrification causes hydrogen peroxide production from hydroxyl radical recombination in sprayed microdroplets

Contact electrification between water and a solid surface is crucial for physicochemical processes at water-solid interfaces. However, the nature of the involved processes remains poorly understood, especially in the initial stage of the interface formation. Here we report that H2O2 is spontaneously produced from the hydroxyl groups on the solid surface when contact occurred. The density of hydroxyl groups affects the H2O2 yield. The participation of hydroxyl groups in H2O2 generation is confirmed by mass spectrometric detection of O-18 in the product of the reaction between 4-carboxyphenylboronic acid and O-18-labeled H2O2 resulting from O-18(2) plasma treatment of the surface. We propose a model for H2O2 generation based on recombination of the hydroxyl radicals produced from the surface hydroxyl groups in the water-solid contact process. Our observations show that the spontaneous generation of H2O2 is universal on the surfaces of soil and atmospheric fine particles in a humid environment.

Automated summary

Contact electrification between water and a solid surface leads to the spontaneous production of H2O2 from hydroxyl groups on the surface. The density of hydroxyl groups affects the yield of H2O2. Mass spectrometry confirms the involvement of hydroxyl groups in the generation of H2O2. A model based on the recombination of hydroxyl radicals from surface hydroxyl groups is proposed. The generation of H2O2 is found to be universal on soil and atmospheric fine particle surfaces in a humid environment.