Effects of Silver Doping in the Structural and Optical Properties of Hematite (α-Fe₂O₃) Synthesized via Chemical Precipitation Method

Hematite (α-Fe2O3) is a low-cost n-type semiconductor with significant absorption of visible light owing to its low bandgap energy of 2.1 eV. The wide applications of hematite in renewable energy and environmental remediation continuously entice more studies. However, the low absorbance of solar energy in the UV-range significantly limits the efficiency of many photocatalytic materials. In this study, we tried to dope α-Fe2O3 with silver via chemical precipitation method to lower the bandgap energy and widen its absorbance. The effects of doping hematite with Ag on the structure, morphology, elemental composition, and optical absorbance were determined by characterizing the samples via X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and UV-Vis spectroscopy, respectively. It was observed from the XRD patterns that the α-Fe2O3 crystallizes in hexagonal structure with lattice parameters a = 5.0380 Å and c = 13.7720 Å for the pure α-Fe2O3. Doping with 0.1M and 0.2M AgNO3 leads to a greater value of the lattice parameters indicating successful doping. SEM images show that the hematite formed was composed of particles with irregular shapes that have sizes in the range 0.865-0.883 μm. Excess silver particles were deposited on the surface of hematite. UV-Vis spectra show that there is a red-shift in the absorption band of the Ag-doped hematite. A notable decrease in the bandgap energy of the undoped α-Fe2O3 was observed from ~2.2eV to ~2.0eV with the increase in the amount of the dopant in the hematite as determined using Tauc's plot. (authors)