Hydrogen peroxide forms spontaneously in water (bulk, film, or microdroplet) via reduction of dissolved oxygen at solid-water interface

TL;DR

This paper challenges previous claims that hydrogen peroxide spontaneously forms in water microdroplets via reduction of oxygen at interfaces, offering an alternative explanation for observed RH-dependent H2O2 levels.

Contribution

It provides an alternative explanation to prior claims of spontaneous H2O2 formation in microdroplets, questioning the causality between humidity and peroxide generation.

Findings

Questions the causality between relative humidity and H2O2 formation.

Proposes an alternative mechanism for observed H2O2 levels.

Highlights the need for further investigation into microdroplet chemistry.

Abstract

Zare and co-workers have recently claimed that hydrogen peroxide is spontaneously generated on the air-water interface of sprayed microdroplets, i.e., that H2O2 forms without an external energy source or co-reactant or catalyst. Specifically, they find that the H2O2(aq) concentration in sprayed microdroplets increases by a factor of 3.5 (or 2.5) as the spray chamber's relative humidity (RH) is changed from 15% to 50% (or from 15% to 95%). Building on these results, they imply causation for the seasonality of viral infections arising from the RH-dependent H2O2 generation in environmental microdroplets. Here, we present an alternative explanation for their observations.