Probing catalyst-free hydroxyl radical generation at microbubble interfaces

Gas–liquid interfaces at the micro- and nanoscale are emerging hotspots for unique chemical reactivity, yet the reactivity of individual microbubbles remains largely unexplored. Here, we visualize the catalyst-free generation of reactive oxygen species, particularly hydroxyl radicals, at the gas‒liquid interface of microbubbles. In-situ chemiluminescence imaging, together with spectroscopic analyses, and multiscale computational simulations shows that the enrichment of hydroxide ions at the microbubble surface, coupled with the interfacial electric field, drives the catalyst-free generation of hydroxyl radicals. The generated hydroxyl radicals enable efficient degradation of organic pollutants and facilitate the conversion of nitrogen into nitrate ions under mild conditions, highlighting the practical applicability of this catalyst-free process in environmental remediation and sustainable nitrogen fixation. These findings provide new insights into catalyst-free radical chemistry at gas–liquid interfaces, with significant implications for catalytic processes, sustainable chemical manufacturing, and environmental catalysis.