The use of the hydrothermal technique in the development of nanomaterials for photocatalysis and solar cells

Abstract

This study investigates the synthesis, characterization, and photocatalytic performance of zinc oxide (ZnO) and magnesium oxide (MgO) nanostructures synthesized using green and hydrothermal methods, with a focus on the influence of pH, doping, and the incorporation of plant extracts. ZnO nanorods (NRs) were synthesized at three different pH values, and X-ray diffraction (XRD) analysis confirmed the formation of high-purity hexagonal Wurtzite-type ZnO. Grain size increased with decreasing pH, and scanning electron microscopy (SEM) confirmed the nanorod morphology. Photocatalytic tests revealed excellent degradation rates of methylene blue (MB) and methyl orange (MO), which increased with the pH value. The degradation rates reached approximately 95% and 64%, respectively, after 30 minutes of UV irradiation. Further enhancement of ZnO NRs was achieved by adding eucalyptus leaf extract, resulting in improved photocatalytic performance, with 94.77% MB degradation after 90 minutes. SEM and transmission electron microscopy (TEM) analyses revealed rod-like structures for green-synthesized ZnO NRs, with XPS confirming the incorporation of biosynthetic impurities. In parallel, MgO nanostructures were synthesized through green methods and chemical doping. XRD analysis revealed a cubic crystal structure . SEM imaging showed a transformation in morphology from plate-like structures in pure MgO to quasi-spherical particles in the green-synthesized samples. Photocatalytic performance was robust, with over 85% dye degradation efficiency after three cycles, driven by hydroxyl radicals. Doping MgO with polyvinylpyrrolidone (PVP) improved colloidal stability and photocatalytic efficiency, However, excessive PVP (?2.5 g) hindered photocatalytic activity by blocking active sites. These results demonstrate the potential of both ZnO and MgO nanostructures for practical and sustainable photocatalytic applications, with green synthesis and doping strategies enhancing their performance and stability