Hydrothermal assisted synthesis of shape-controlled zinc oxide nanostructures for tuneable photodegradation of methylene blue pollutant

Abstract

In this study, we have investigated the effects of EDTA, citric acid, and urea on the morphology-controlled synthesis of ZnO nanostructures by a hydrothermal method. XRD, FTIR, FESEM, TEM, BET, and UV-DRS studies revealed that the addition of different complexing agents not only controls the size and morphology but also alters the crystallinity, particle size, energy bandgap, specific surface area, and pore characteristics of ZnO. We achieved diverse morphologies, including spherical nanoparticles (80–100 nm), nanorods (1 µm length, 100 nm diameter), and nanoflakes (100–200 nm lateral dimension with 10–20 nm thickness) utilizing citric acid, urea, and EDTA as morphology controllers. The resulting nanoparticles had surface areas of 11.8 m²/g, 29.6 m²/g, and 4.6 m²/g, respectively. ZnO nanostructures developed with citric acid, urea, and EDTA were found to have a band gap of 3.273 eV, 3.209 eV, and 3.380 eV, respectively. The photodegradation efficiency of ZnO spherical nanoparticles, nanorods, and nanoflakes was found to be 90%, 97%, and 81%, respectively, demonstrating the shape-dependent photodegradation of MB dye. The prepared ZnO photocatalyst exhibits pseudo-first-order kinetics with good recyclability (five cycles) and stability. The enhanced photocatalytic performance of ZnO nanorods was attributed to their morphology, which facilitates efficient charge separation and increased surface area, leading to more active sites for pollutant degradation. This study offers a potential approach for developing morphology-driven photocatalysts for environmental remediation and water purification.

Graphical Abstract