Water microdroplets spontaneously produce hydrogen peroxide

Researchers at Stanford University have recently found that microscopic droplets of water spontaneously – and unexpectedly – produce hydrogen peroxide, a molecule known to be a common bleaching agent and disinfectant.

The discovery was made by chance, while scientists were undertaking research to find a new, more efficient way of creating gold nanostructures in tiny water droplets (microdroplets). To make these structures, the team added an additional molecule known as a reducing agent. As a control test, they assessed whether they could create gold nanostructures without the reducing agent being present. Whilst theoretically this should have been impossible, it worked anyway, thus hinting at an, as of yet, undiscovered feature of microdroplet chemistry. This allowed them to trace these results to the presence of the molecule hydroxyl – comprised of a single hydrogen atom paired with an oxygen atom – which could also act as a reducing agent. This is in turn led the team to postulate as to whether hydrogen peroxide, which is a molecule made up of two hydrogen and two oxygen atoms, was also present.

By conducting a series of tests, the researchers concluded that water microdroplets spontaneously form hydrogen peroxide, and that smaller microdroplets produce higher concentrations of the molecule. To explain this seemingly perplexing phenomenon, they hypothesised that ‘a strong electric field near the surface of water microdroplets in air triggers hydroxyl molecules to bind into hydrogen peroxide’.

Hydrogen peroxide is an important commercial and industrial chemical, mainly manufactured through an ecologically unfriendly process. These findings could therefore have significant practical consequences, helping to make such methods greener and leading to simpler ways of disinfecting surfaces: ‘simply spraying water microdroplets on a table or floor might be enough to clean it’.

Applicants for Chemistry may reflect on this scientific breakthrough, contemplating how it could potentially be used to foster innovation in paving the way for greener, more sustainable ways of producing the molecule.