Evaluation of passive NO₂ removal by graphene oxide-polyacrylonitrile electrospun nanofiber membranes at indoor-relevant concentrations

Traffic-related outdoor nitrogen dioxide (NO₂) emissions can infiltrate indoor environments, negatively affecting indoor air quality (IAQ), particularly in buildings near urban roads. In the present exploratory study, the passive performance of graphene oxide (GO)-doped polyacrylonitrile (PAN) electrospun nanofiber filters (GOPAN) for NO₂ removal was investigated under controlled conditions representative of indoor exposure to traffic-related pollution. GOPAN nanofibers were fabricated with varying GO concentrations (0.5-3 wt%) to evaluate the effect of the GO loading on passive indoor NO₂ removal performance. Chamber-scale experiments were conducted under controlled indoor environmental conditions using NO₂ concentrations representative of urban outdoor exposure levels. Among all tested GOPAN nanofiber filters, the 2 wt% GO-doped filter (2GOPAN) achieved the highest passive NO₂ removal efficiency of approximately 31%. The results demonstrate that the moderate incorporation of GO may improve the passive interaction of PAN-based electrospun membranes with NO₂ at concentrations representative of urban outdoor exposure levels. The chamber experiment is an initial screening of materials, not a direct simulation of airflow through an open window. However, the relatively low clean air delivery rates (CADR) indicate that substantial improvements in material performance are required for practical large-scale applications and highlight the strong limitation of passive air cleaning by diffusion-controlled mass transfer under indoor conditions.