Cascade co-polarized hydro-charged nanofibers enable long-term and harsh-environment-tolerant air filtration

Particulate matter, along with outbreaks of infectious disease, has created a high demand for air filtration materials for personal protection. However, mainstream electret melt-blown filters suffer from both structural defects at the micron diameter scale and the technical drawback of separate processes for fiber forming and charging, failing to remove particles effectively and durably. Herein, cascade polarized nanofibrous membranes are constructed via an in situ hydro-charging strategy. Based on a creative perspective of high-speed electrospinning jets having a friction electrification effect with pure water, both outer and inner hydro-charging methods are adopted, resulting in polyvinylidene fluoride (PVDF) nanofibers with micro- and macro-polarized structures. Benefitting from unique cascade polarization, PVDF hydro-charged electrospun fibers (HCEFs) exhibit high filtration efficiency towards PM_0.3 (99.43%), a low pressure drop (41.7 Pa) and high surface potential (6037 V). HCEFs also show stable filtration performance when exposed to acid vapor, alkali vapor, and a high-humidity environment. This strategy may shed light on preparing next-generation high-performance electret filtration materials.