Author: B. G. Meriya, S. P. Das, J. J. Boruah

DOI: http://doi.org/10.31788/RJC.2026.1949890

ZnO-based nanocatalysts with defect-engineered oxygen vacancies were designed and studied to produce biodiesel. Pristine ZnO, Na-incorporated ZnO (Na–ZnO), and Mg-incorporated ZnO (Mg-ZnO) nanoparticles were preparedthrough a sustainable route by using Aloe vera extract and systematically characterised by elemental analysis, atomic absorption spectroscopy (AAS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy- energy-dispersive X-ray analysis (SEM-EDX), powder X-ray diffraction (XRD), and UV-Vis diffuse reflectancespectroscopy. Of these, the XPS analysis offered clear experimental data on the greatly improved oxygen vacancyconcentration in Na- and Mg-modified ZnO, which meant the effective defect engineering under the influence of theincorporation of the heteroatoms. The catalytic activity was tested in the transesterification of fresh and usedsunflower oils, and the catalytic activity was strongly related to the level of oxygen vacancies. Mg-ZnOdemonstrated better catalytic performance with biodiesel yields of 96 per cent (fresh oil, 1 h), 88 per cent (used oil, 1h) and then Na-ZnO (81 per cent and 68 per cent in 1.5 h), and pristine ZnO (62 per cent and 48 per cent in3h). This increased reactivity (ZnO < Na–ZnO < Mg–ZnO) has been ascribed to the electronic modulation via oxygenvacancies, which facilitates reactant adsorption, triglyceride activation and surface basicity. Thus, the present workdemonstrates the essential importance of oxygen vacancies as active sites in ZnO-based nanocatalysts and gives asensible approach to making catalysts with the greatest performance in the generation of biodiesel on a sustainablebasis.

Keywords: Green Synthesis, Na-doped ZnO, Mg-doped ZnO, Aloe Vera Extract, Biodiesel Production.