Self‐Pumped Hygroscopic Nanofiber Emitter for Ozone‐Free Water Electrospray‐Based Air Purification

Abstract Indoor air purification technologies encounter inherent trade‐offs among efficiency, safety, and scalability. Conventional filter‐based systems are hindered by increasing pressure drop and frequent maintenance, whereas filterless electrostatic precipitators produce hazardous ozone due to corona discharge and demand high operating voltages. Here, a compact ozone‐free air purification system is demonstrated, which utilizes water electrospray driven by a self‐pumped hygroscopic nanofiber emitter. The emitter comprises an electrospun organic–inorganic composite membrane of poly(vinyl alcohol), poly(acrylic acid), and montmorillonite. This hybrid structure integrates the hygroscopic and chemically active properties of the polymers with the mechanical reinforcement of the inorganic filler, enabling continuous capillary‐driven water transport. The hygroscopic emitter autonomously transports water to the emission tip, enabling stable cone‐jet electrospray without external pumps. A ring‐shaped extractor electrode concentrates the local electric field, thereby sustaining water electrospray below 5 kV. In a 0.1 m 3 sealed chamber, the device achieves over 97% removal of PM 0.3 within 5 min across 30 repeated operation cycles, while maintaining ozone levels below 20 ppb and water consumption under 0.4 mL h −1 per emitter tip. These results establish hygroscopic nanofiber‐based electrospray emitters as a safe, energy‐efficient, and scalable platform for filterless indoor air purification.