Construction of F-doped Co3O4/Co3O3.69F0.31 nanocomposite for boosting photocatalytic removal of organics from industrial waste H2O under visible-light

Visible-light (λ ≥ 420 nm) active fluorine (F) doped composite photocatalyst Co 3 O 4 /Co 3 O 3.69 F 0.31 was prepared through substitution method. In this process, cobaltic oxide, Co 3 O 4 was synthesized first; subsequently, F was introduced into Co 3 O 4 . The prepared Co 3 O 4 /Co 3 O 4-x F x heterocomposite photocatalysts were characterized through X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), EDX-mapping, UV–visible Spectrophotometry, X-ray Photoelectron Spectroscopy (XPS). Zeta potential indicates that the photocatalysts carrying negative charge on its surface which make the catalyst more suspended compare to undoped Co 3 O 4 . The Co 3 O 4 /Co 3 O 4-x F x composite with several atom % of F demonstrated better photocatalytic activity compare to Co 3 O 4 and TiO 2 nanoparticles towards the decomposition of methyl blue (MB) and phenol in aqueous medium under visible light irradiation. The composition of Co 3 O 4 /Co 3 O 4-x F x was optimized to 0.31 atom% (i.e., x = 0.31) of F doping with respect to degradation of organics in aqueous medium. After 2 h of visible irradiation, 33% decomposition MB and 45% degradation of phenol were achieved with Co 3 O 4 /Co 3 O 3.69 F 0.31 composite photocatalyst whereas, Co 3 O 4 and TiO 2 demonstrated negligible decomposition efficiency. Due to F doping, the valence band (VB) level of Co 3 O 4 was up-lifted which enhanced the absorption of visible light and made possible excitation of more and more VB electrons Co 3 O 4 /Co 3 O 3.69 F 0.31 towards its conduction band (CB) and, thus CB electrons (e − ) and VB holes (h + ) are spatially separated. Experimental study proved that both the excited electrons (e − ) and holes (h + ) of Co 3 O 4 /Co 3 O 3.69 F 0.31 composite took part in degrading photocatalytic reactions as well as enhanced photocatalytic efficiency.