Co+2, Ni+2, Cu+2 doped Indium oxide as visible active nano-photocatalyst: A facile solution combustion synthesis, electronic band structure analysis by DFT approach and photocatalytic decontamination of RhB and Triclopyr

The present investigations deals with the fabrication of metal ion (M = Co+2, Ni+2, and Cu+2) doped-In2O3 photocatalysts by a simple solution combustion method. All the synthesized materials were characterized for different features by various techniques including XRD, FESEM, EDX, XPS, UVDRS, and PL. Synthesized compounds were examined for the degradation of two organic pollutants; cationic dye Rhodamine B (RhB) and pesticide Triclopyr (TC). Modification with metal ions significantly improved the degradation efficiency of pure In2O3 photocatalyst and followed the trend Co+2/In2O3 > Ni+2/In2O3 > Cu+2/In2O3 > In2O3. Highest degradation efficiencies of 99.03% for RhB and 95.84 % for TC were obtained in the case of Co+2/In2O3 (1 mol %) under visible light illumination. Further, Density Functional Theory investigations show that Co+2/In2O3 is the most favorable energetically and leads to the creation of two transition states -as opposed to a single transition state in the other doped systems-, one of which is near the Fermi level and the other at around 1.5 eV above it. We believe that this exclusive property is behind the highest photocatalytic efficiency observed experimentally. Additionally, the doped nanostructures lead to higher visible light absorption and separation of light induced charge carriers. The effect of the pH and the reactive oxygen species were also examined. Besides, a probable mechanism of charge transfer and degradation of the pollutants was presented.