Work

Disentangling the Roles of Dissolved Oxygen, Common Salts, and pH on Spontaneous Hydrogen Peroxide Production in Water: No O 2 , No H 2 O 2

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Despite mounting evidence that the air–water interface or microdroplet geometry has no bearing on the spontaneous formation of hydrogen peroxide (H 2 O 2 ) down to a 50 nM limit of detection, the debate persists. Recent studies have demonstrated connections between the spontaneous formation of hydroxyl (HO • ) radicals and H 2 O 2 in sprayed microdroplets and the solution pH, dissolved salts, nebulizing gas, and gaseous environment. Among the halides, chloride (Cl – ), bromide (Br – ), and iodide (I – ), the studies found that Br – dominated H 2 O 2 formation because of its enhanced fractionation at the air–water interface and ability to donate electrons. The studies also suggested that H 2 O 2 production at the air–water interface scales with the alkalinity of water. In response, this report employs a comprehensive set of techniques, encompassing nuclear magnetic resonance, potentiodynamic polarization, electron microscopy, and H 2 O 2 assay kit fluorometry, to examine these claims. The experiments reveal that the air–water interface or microdroplet geometry does not drive H 2 O 2 formation, regardless of the presence of halide in water. The reduction of oxygen gas (O 2 ) at the solid–water interface produces H 2 O 2 (i.e., in the absence of O 2, no H 2 O 2 is formed regardless of the halide). This work explains the relative dependence of H 2 O 2 concentrations on halides based on their propensity to drive pitting corrosion (Cl – > Br – > I – ). As pits appear in the passivating layer, exposing the metal, H 2 O 2 is consumed during further oxidation. This work also disproves the claim that alkalinity drives H 2 O 2 formation, as it demonstrates that aluminum and titanium surfaces generate higher H 2 O 2 concentrations in acidic and alkaline conditions, respectively. Taken together, this report provides alternate explanations for the observations that should help draw the debate toward its closure.

Source: Journal of the American Chemical Society

DOI: 10.1021/jacs.5c09028

Authors: Muzzamil Ahmad Eatoo, Himanshu Mishra

Institution: King Abdullah University of Science and Technology

Language: English

Topic: Minerals Flotation and Separation Techniques

Subfield: Water Science and Technology

Field: Environmental Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: King Abdullah University of Science and Technology, Water Desalination and Reuse Center, King Abdullah University of Science and Technology