Indium doped and carbon modified P25 nanocomposites with high visible-light sensitivity for the photocatalytic degradation of organic dyes

• Photocataysts were employed to decolorize both cationic MB and anionic RR4 dye respectively.
• Degradation efficiency and hydrogen evolution rate was over 90% and 2.44 mmol g−1 respectively.
• Removal efficiency by In/C-P25 was sustainable and stable after 5 times of repeated usage.
• The effects of initial pH values on MB and RR4 solution for photocatalysts was investigated.

The commercially available TiO2 Degussa P25 was modified using a simple technique to produce a visible-light-actived indium and carbon doped P25 catalyst. The modified photocatalysts have been successfully obtained by thermal heating method. These as-obtained products were successfully characterized by X-ray diffraction (XRD), X-ray photoelectrion spectroscopy (XPS), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy respectively. The photocatalytic activities of all prepared catalysts were evaluated by the degradation of organic dyes including methylene blue (MB) and Reactive Red 4 (RR4) under visible light irradiation. As the result shown, the indium and carbon co-doped on P25 nanocomposites possessed the extended light absorption in visible light and better charge separation capability as compared to the pristine P25. The optimum loading of In3+ ions on P25 was 15%. Moreover, 15% In2O3/C-P25 showed the highest degradation rate of organic dye, which the removal efficiency can reach over 90% after 90 min and the corresponding hydrogen evolution rate of 15% In2O3/C-P25 was 9 times than P25. It was concluded that the synergistic effects of In3+ ions and carbon narrowed the band gap of TiO2 and promoted charge separation, which played a significant role for the enhancement of photoactivity. In addition, it was observed that the photo-degradation for all catalysts followed the first order reaction kinetics. Furthermore, the influence of initial pH values on the photocatalytic degradation of MB and RR4 using 15% In2O3/C-P25 catalyst was also investigated. Finally, the stability test of photocatalysts was carried out and the photocatalytic mechanism was explained concretely.

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