One-step electrodeposition and fractal analysis of a novel Ni-graphene superhydrophobic coating

A novel superhydrophobic Ni-graphene coating was synthesized by one-step electrodeposition without low surface energy modification. The two-dimensional and three-dimensional morphology were investigated by scanning electron microscope, atomic force microscope, and confocal profilometry. Combining fractal theory and power spectral density analysis, the structural characteristics of the coating surface were quantified by key surface parameters. By building the numerical relationship between surface structure and wetting property, the coating-water contact mode was identified according to the measured contact angle and fractal contact angles calculated from Cassie and Wenzel theories. Additionally, the optimized deposition parameters and the role of graphene on the coating structure were also pinpointed. The results show that the Ni-graphene coating deposited at graphene oxide concentration of 0.20 g·L−1 and deposition current density of 40 mA·cm−2 exhibited dual-level fractal structure in micro- and nano-scales. The Ni-graphene superhydrophobic coating possessed a water contact angle of 156.1° ± 0.6°, a sliding angle of 6.2° ± 0.8°, as well as self-cleaning characteristics, and the wetting system was confirmed to follow the Cassie contact mode.