Al and Li co-doping effects on structural, band-gap, and photocatalytic properties of pyro-hydrolyzed ZnO nano-powder

Abstract Li (0–10 wt%) and Al (0–0.5 wt%) co-doped ZnO nano powders were synthesized following a sol-gel solution pyro-hydrolysis route at 450 °C, and were thoroughly characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy dispersed analysis with X-rays (EDAX), diffuse reflectance spectroscopy (DRS), ultra-violet visible spectroscopy (UV–vis.), Fourier-transform infrared (FT-IR), Fourier-transform Raman spectroscopy (FT-Raman), thermo-gravimetry (TGA)-differential scanning calorimetry (DSC), BET surface area, zeta potential ( ζ ) analysis and others. The characterization results suggest that the powders formed in this pyro-hydrolysis route are in well-crystalline wurtzite phase, thermally stable, and possess reasonably high specific surface area, fine crystallite size, high negative zeta potential values, low band-gap energy and direct band-gap energy transition states. Upon doping with 0.5 wt% Al, a drastic reduction in the crystallite size of Li (0.2–10 wt%)-doped ZnO powder was noted. The Al and Li co-doped ZnO powders exhibited an appreciable photocatalytic activity in the methylene blue (MB) degradation reaction while following the Langmuir-Hinshelwood first order reaction-rate relationship.