Synergism of oxygen vacancy and carbonaceous species on enhanced photocatalytic activity of electrospun ZnO-carbon nanofibers: Charge carrier scavengers mechanism

•ZnO-carbon nanofibers higher photocatalytic activity under UV and visible light.•The synergy between oxygen vacancy and carbonaceous species were discussed.•Oxygen vacancy caused band gap energy reduction in the ZnO-carbon nanofibers.•Photo-generated electrons acted as the main photo-oxidation pathway.•Carbonaceous species as a photosensitizer caused visible photocatalytic activity. Novel ZnO-carbon and ZnO nanofibers were fabricated by electrospinning of polymer precursor followed by subsequent annealing in nitrogen and air, respectively. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) indicated the smooth and beadless nanofibers with wurtzite crystal structure. X-ray photoelectron spectroscopy (XPS) showed the presence of oxygen vacancies (VO) and chemisorbed O2 on the surface of the samples. Band gap narrowing of the ZnO-carbon nanofibers in comparison to ZnO were measured by diffuse reflectance spectroscopy (DRS). Photo-degradation of azo dye under the UV and visible light was evaluated and ZnO-carbon showed an enhancement in photocatalytic activity due to the presence of carbonaceous species and oxygen vacancies. Formation of hydroxyl radical during the photocatalytic process was verified by the formation of carbon using photoluminescence (PL) analysis. The photocatalytic mechanism was investigated by measuring the degradation rate in the presence of tert-butyl alcohol (t-BuOH) and I− anion as OH radical and hole (h+) scavenger. The results indicated photo-generated electrons are the main photo-oxidation pathway.