Accelerated Pollutant Degradation by UV/H₂O₂ at the Air–Water Interface of Microdroplets

Ultraviolet light-induced homolysis of hydrogen peroxide (UV/H₂O₂) can generate powerful hydroxyl radicals (^•OH) for sustainable water purification. However, the efficiency of the conventional bulk-phase UV/H₂O₂ system is limited by the low yield and utilization of ^•OH, in turn necessitating high UV energy input and long purification period. In this study, we present an innovative UV/H₂O₂ microdroplet system for enhanced pollutant degradation. The degradation of pollutants in sprayed microdroplets was accelerated by 8.5-63.3-fold compared to those in bulk water, demonstrating universal effectiveness across a range of pollutant types and diverse aqueous matrices. This enhancement stems from elevated ^•OH production at the air-water interface due to the enhanced UV absorbance of H₂O₂. The production of ^•OH in the microdroplet system was 45-fold higher than that in bulk water, facilitating rapid ^•OH-mediated pollutant degradation. Moreover, pollutants accumulate at the air-water interface, where ^•OH is concentrated, leading to higher utilization of ^•OH for mediating pollutant degradation before quenching. Our findings provide a solution to overcome the bottlenecks in ^•OH production and utilization, offering insights for improving the efficiency of UV/H₂O₂ water treatment systems.