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

Abstract

Visible-light (λ ≥ 420 nm) active fluorine (F) doped composite photocatalyst Co3O4/Co3O3.69F0.31 was prepared through substitution method. In this process, cobaltic oxide, Co3O4 was synthesized first; subsequently, F was introduced into Co3O4. The prepared Co3O4/Co3O4-xFx 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 Co3O4. The Co3O4/Co3O4-xFx composite with several atom % of F demonstrated better photocatalytic activity compare to Co3O4 and TiO2 nanoparticles towards the decomposition of methyl blue (MB) and phenol in aqueous medium under visible light irradiation. The composition of Co3O4/Co3O4-xFx 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 Co3O4/Co3O3.69F0.31 composite photocatalyst whereas, Co3O4 and TiO2 demonstrated negligible decomposition efficiency. Due to F doping, the valence band (VB) level of Co3O4 was up-lifted which enhanced the absorption of visible light and made possible excitation of more and more VB electrons Co3O4/Co3O3.69F0.31 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 Co3O4/Co3O3.69F0.31 composite took part in degrading photocatalytic reactions as well as enhanced photocatalytic efficiency.