Tailoring the Preparation, Microstructure, FTIR, Optical Properties and Photocatalysis of (Fe/Co) Co-Doped ZnO Nanoparticles (Zn0.9FexCo0.1−xO)

In this work, Fe3+- and Co2+-doped ZnO NPs (zinc oxide nanoparticles), Zn0.9FexCo0.1−xO, with a hexagonal wurtzite phase (single-phase), were synthesized via a co-precipitation technique where the phase purity and elemental composition were confirmed by XRD and EDX, respectively. Due to the substitution of Fe by Co, the cell parameters (a and c) were increased, alongside which a slight shift to higher diffracted angles appeared. FTIR was carried out to confirm the insertion of both the Fe3+ and Co2+ dopants into the ZnO hexagonal phase. Based on the experimental results, different numerical techniques were used to determine the optical gap and refractive index for the ZnO NP-doped samples, and when the concentration of Fe3+ ions was increased, the band gap value of ZnO decreased from 3.36 eV to 3.29 eV, accompanied by a decrease in the Urbach energy, while the refractive index increased. The doped ZnO NPs were later found to be effective UV photocatalysts which demonstrated a maximum reduction (84%) of methylene blue (MB) in a neutral environment for X = 0.05. The correlation between the Fe3+ concentration, structure, optical parameters, and photocatalytic efficacy is explained in detail.