Harnessing air-water interface to generate interfacial ROS for ultrafast environmental remediation

The air-water interface of microbubbles represents a crucial microenvironment that can dramatically accelerate reactive oxidative species (ROS) reactions. However, the dynamic nature of microbubbles presents challenges in probing ROS behaviors at the air-water interface, limiting a comprehensive understanding of their chemistry and application. Here we develop an approach to investigate the interfacial ROS via coupling microbubbles with a Fenton-like reaction. Amphiphilic single-Co-atom catalyst (Co@SCN) is employed to efficiently transport the oxidant peroxymonosulfate (PMS) from the bulk solution to the microbubble interface. This triggers an accelerated generation of interfacial sulfate radicals (SO₄^•-), with 20-fold higher concentration (4.48 × 10^-11 M) than the bulk SO₄^•-. Notably, the generated SO₄^•- is preferentially situated at the air-water interface due to its lowest free energy and the strong hydrogen bonding interactions with H₃O⁺. Moreover, it exhibits the highest oxidation reactivity toward gaseous pollutants like toluene, with a rate constant of 10¹⁰ M^-1 s^-1-over 100 times greater than bulk reactions. This work demonstrates a promising strategy to harness the air-water interface for accelerating ROS-induced reactions, highlighting the importance of interfacial ROS and its potential application.