Synthesis and characterization of Al-doped ZnO nanorod array as a photocatalyst under visible light irradiation

Al-doped ZnO NR arrays were successfully synthesized using a low-temperature (∼90 °C) microwave-assisted hydrothermal method. The visible-light-driven photocatalytic performance of NRs was investigated as function of doping and the pH of the growth solution. Both parameters significantly influence the morphology, crystal structure, surface composition, optical and electronic properties of NRs. Particularly, Al doping led to enhanced visible light absorption, with further improvement observed in samples grown in alkaline media. The combined effect of doping and pH also induced a morphological transition from rod-like to obelisk-shaped NR nanostructures. Molecular dynamic simulation revealed that positively charged MB molecules preferentially adsorb onto the negatively charged O-terminated polar facets of ZnO NRs through electrostatic interactions. For NRs grown in neutral pH, Al doping results in enhanced photocatalytic activity, which correlates closely with the improved visible light absorption. In contrast, NRs grown in alkaline media exhibit comparable efficiencies, influenced by their optical absorption and modified morphology. Among the tested samples, AZO 1 % sample demonstrated the highest performance, achieving 52 % degradation of MB under low-intensity visible light LED illumination. The degradation reaction rate for this sample is three times higher than that of undoped ZnO NRs.