Hydrocarbon Degradation by Contact with Anoxic Water Microdroplets

Oils are hydrophobic, but their degradation is frequently found to be accelerated in the presence of water microdroplets. The direct chemical consequences of water-oil contact have long been overlooked. We show that aqueous microdroplets in emulsified water-hexadecane (C₁₆H₃₄) mixtures can spontaneously produce CO₂, •H, H₂, and short-chain hydrocarbons (mainly C₁ and C₂) as detected by gas chromatography, electron paramagnetic resonance spectroscopy, and mass spectrometry. This reaction results from contact electrification at the water-oil microdroplet interface, in which reactive oxygen species are produced, such as hydrated hydroxyl radicals and hydrogen peroxide. We also find that the H₂ originates from the water microdroplet and not the hydrocarbon it contacts. These observations highlight the potential of interfacial contact electrification to produce new chemistry.