Freezing-Thawing-Induced Hydrogen Peroxide Formation in PFA Containers

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Reactive oxygen species (ROS), including hydrogen peroxide (H2O2), are known to form at aqueous interfaces under dark conditions.
• The precise mechanisms driving H2O2 formation at interfaces, particularly during phase transitions, remain incompletely understood.

Purpose of the Study:

• To investigate the generation of H2O2 during the freezing and thawing of water in fluorinated polymer containers.
• To elucidate the factors influencing H2O2 formation, such as the number of freeze-thaw cycles, polymer type, salt concentration, dissolved oxygen, and temperature.

Main Methods:

• Utilized perfluoroalkoxy polymer (PFA) and polypropylene (PP) tubes for water freezing and thawing experiments.
• Quantified H2O2 production across varying numbers of freeze-thaw cycles, salt concentrations, and temperatures.
• Conducted experiments in an ozone-free glovebox to assess the role of dissolved oxygen.

Main Results:

• Demonstrated H2O2 generation in PFA containers upon freezing and thawing without external electrical bias or agitation.
• Observed a near-linear increase in H2O2 formation with the number of freeze-thaw cycles.
• Found that H2O2 yield is significantly higher in PFA compared to PP tubes and is dependent on salt concentration, dissolved oxygen, and temperature extremes.

Conclusions:

• Freezing and thawing of water in PFA containers is a novel pathway for H2O2 generation.
• This phenomenon is influenced by interfacial charge transfer and requires dissolved oxygen.
• Findings have implications for interpreting ROS measurements and understanding redox processes in freezing aqueous systems.