Microwave-assisted synthesis of various Cu2O/Cu/TiO2 and CuxS/TiO2 composite nanoparticles towards visible-light photocatalytic applications

Microwave-assisted Cu2O/Cu/TiO2 and CuxS/TiO2 composite nanoparticles were successfully prepared with or without several kinds of supporting chemical linkers between Cu and Ti. As for the synthesis of cube-shaped Cu2O/Cu/TiO2 composite nanoparticles, mixed alcohols containing ethyl alcohol and benzyl alcohol were used without any additives under 800–900 W microwave. CuxS/TiO2 composite particles were prepared using two kinds of experimental procedures. One method was to use l-cysteine additive to interconnect TiO2 and CuxS in neutral aqueous solution. The other method was to use thiourea under NaOH basic condition. The particle morphology was confirmed with TEM images and the homogeneous distribution of elements including Ti, O, Cu, and S were proved by TEM-EDS mapping method. XRD patterns clarified high crystallinity of anatase TiO2 and Cu salts. Crystal structures of Cu2O and CuxS varied depending on the relative compositions and synthetic procedures. UV–visible spectra showed high absorbance at visible region according to the Cu species incorporated in the composite particles. The photocatalytic performance of each composite sample was compared both by monitoring the degradation of Rhodamine B under UV irradiation and methyl orange under visible-light irradiation. Under UV irradiation, the amount of copper species seems to hinder the catalytic performance, whereas Cu2O and Cu inside ternary Cu2O/Cu/TiO2 composites enhance the performance under visible-light irradiation.