Influence of molybdenum on structural, morphological, optical and electrochemical properties of ZnO nanoparticles

The present research explores the addition of molybdenum (Mo)-doped ZnO nanoparticles synthesized using a hydrothermal method. The initial goal of the study is to remove the inherent downsides of pristine ZnO nanostructures corresponding to low electrical conductivity and low electrochemical activity by defect engineering. Pure ZnO nanomaterials were enriched with 2-percent (mol) of Mo and characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, photoluminescence (PL), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The XRD analysis indicated the formation of single-stage hexagonal wurtzite ZnO with the successful addition of Mo in the lattice as well as contraction of the lattice, decreased crystallite size (between 30 nm and 22 nm) and increased microstrain. The morphological analysis showed that the agglomeration is lower and increased heterogeneity on the surface of the doped sample. Optical studies revealed that the defect induced intermediate energy states between 3.5 eV and 3.7 eV, with the blue-shift of the absorption edge and increased bandgap of 3.5 eV to 3.7 eV. The photoluminescence measurements further proved the high defect density by the suppression of near-band-edge emission and high deep-level emissions. The electrochemical analysis demonstrated that the performance of Mo-doped ZnO has significantly improved, and a reduced resistance to charge transfer (7.7 kΩ). These enhancements have arisen due to the defect-assisted pseudocapacitive behavior, increased electroactive sites and improved charge transfer kinetics. The specific capacitance for pure and Mo-doped ZnO nanostructure was called 78 F/g and 91 F/g respectively. Finally, the present study demonstrates that dopant-induced structural changes and multifunctional behavior are directly correlated with Mo-doped ZnO, which makes such material a promising candidate to be used in energy storage, optoelectronics and sensing applications.