Continuous fabrication of hollow photocatalytic CNT/TiO₂/calcium alginate microfibers via needle-based microfluidic device for environmental remediation in NO removal

NO is a common harmful air pollutant which leads to various environmental and health problems and needs to be addressed urgently. Herein, by combining sol-gel method and microfluidic approach, we successfully developed novel hollow alginate microfibers containing CNT/TiO₂ photocatalysts. The resulting fibers, with diameter of 1000 μm and adjustable wall thickness of 60–150 µm, were confirmed through microscope and SEM. The formation condition about various flow rate ratios of different phases was also investigated. Subsequently, various characterization methods including XRD, FT-IR and XPS were employed to investigate structural properties of prepared CNT/TiO₂ hybrid materials. Our findings indicate that the boosted absorption ability towards the visible light region, improved photo-generated electron transfer efficiency, as confirmed by UV–vis spectroscopy and electrochemical impedance respectively, mainly account for the enhanced photocatalytic performance in NO oxidation. The optimized CNT(10 %)/TiO₂ microfibers exhibited the best NO removal efficiency of 44.3 % under visible light, which is 1.59 times that of the pure TiO₂. This study represents an interesting case for the combined preparation of CNT/TiO₂/alginate microfibers for NO abatement.