Spontaneous Production of H<sub>2</sub>O<sub>2</sub> at the Liquid–Ice Interface: A Potential Source of Atmospheric Oxidants
Junwei Song, Laura Werner, Yoan Carreira Mendes Da Silva, Alexander Theis, D. J. Donaldson, C. George
Abstract
High Resolution Image Download MS PowerPoint Slide We present experimental evidence for the spontaneous production of hydrogen peroxide (H 2 O 2 ) at the liquid–ice interface during the freezing of dilute salt solutions. Specifically, sample solutions containing NaCl, NaBr, NH 4 Cl, and NaI at concentrations between 10 –6 and 10 –1 M were subjected to freezing–melting cycles and then analyzed for H 2 O 2 content. The relationship between the production rate of H 2 O 2 and the salt concentration follows that of the Workman–Reynolds freezing potential (WRFP) values as a function of the salt concentration. Our results suggest that H 2 O 2 is formed at the liquid–ice interface from the self-recombination of hydroxyl radicals (OH·), produced from the oxidation of hydroxide anions due to the high electric field generated at the aqueous–ice interface under the WRFP effect. Furthermore, the involvement of O 2 likely acting as an electron capturer could promote to produce more OH radicals and hydroperoxyl radicals (HO 2 ·), thus enhancing the production of H 2 O 2 at the liquid–ice interface. Overall, this study suggests a novel mechanism of H 2 O 2 formation in ice via its spontaneous production at the liquid–ice interface, induced by the Workman–Reynolds effect.