Immobilization of rGO/ZnO hybrid composites on the Zn substrate for enhanced photocatalytic activity and corrosion stability

In this study, a plasma electrolytic oxidation (PEO) process was used to the immobilization of the reduced graphene oxide (rGO)/zinc oxide (ZnO) hybrid on the zinc substrate. The microstructural and compositional characteristics confirmed the successful formation of the rGO/ZnO hybrid composite coatings immobilized on the zinc substrate with crater-like surface morphology. By increasing the content of rGO nanosheets incorporation, the average surface roughness and porosity of the hybrid coatings were found to decrease, compared to the ZnO coating, resulting in a superior hydrophobic behavior of the samples. The investigation on the optical properties of coatings revealed a gradual decrease in the band gap energy with the increment of the rGO content. The photocatalytic activity of the immobilized composite coatings was studied by evaluating the photodegradation kinetics of methylene blue dye under ultraviolet illumination. The degradation reaction rate constant of the hybrid coatings was found to be about 2.3 times higher than that of the ZnO coating. Investigating the corrosion stability, the corrosion current density of the coatings significantly decreased from 741.3 to 0.23 nA.cm⁻², with the increment of rGO nanosheets content. Besides, the Mott-Schottky analysis showed the lower donor density for the hybrid coatings to the account of the unprecedented optical response and high specific surface area of the incorporated rGO nanosheets. Therefore, the immobilization of rGO/ZnO hybrid composites on the zinc substrate using the PEO process can be an effective way to develop an emerging generation of photocatalytic systems with high performance and excellent durability.