Efficient photocatalytic performance enhancement in Co-doped ZnO nanowires coupled with CuS nanoparticles

Highlights: • Photocatalytic properties of ZnO nanowires were improved by combing Co²⁺ doping and CuS coupling. • The photocatalytic enhancement can be ascribed to their synergistic effect. • The amount of CuS nanoparticles has a determining influence on its photocatalytic performance. • Optimum sample is three times efficient compared with pure ZnO nanowires. In this research, a kind of highly efficient semiconductor photocatalyst was fabricated by depositing CuS nanoparticles uniformly on the surface of Co-doped ZnO nanowires. ZnO nanowires were synthesized by hydrothermal method and CuS nanoparticles were modified by successive ionic layer adsorption and reaction (SILAR). By conducting methyl orange (MO) degradation experiments under the illumination of visible light, the photocatalytic activity of Co-doped ZnO nanowires modified with CuS nanoparticles was found to be nearly three times active when compared to bare ZnO nanowires. Its superior photocatalytic performance has two main reasons. The doped Co²⁺ ions can inhibit the recombination of photo-generated electron–hole pairs and decrease the optical bandgap, while the p-n heterostructure can enhance the visible light absorption ability and promote the separation of photo-excited charge carriers. Furthermore, the effect of the amount of deposited CuS nanoparticles on the photocatalysis was also investigated. The photocatalytic efficiency firstly raised along with the increment of SILAR cycle times and reached a maximum at 10 cycles but then decreased as the cycle times continue to increase. This originates from that an excessive amount of CuS would not only cover the active reacting sites, but also serve as recombination centers. Overall, this new nanostructure is expected to work as an efficient photocatalyst.