Bimetallic FeO_x–MO_x Loaded TiO₂ (M = Cu, Co) Nanocomposite Photocatalysts for Complete Mineralization of Herbicides

Abstract

A series of monometallic and bimetallic cocatalyst(s), comprising FeO x , CuO x , CoO x , FeO x −CuO x , and FeO x −CoO x loaded TiO 2 catalysts prepared by the surface impregnation method, were investigated for the photocatalytic mineralization of the widely used four herbicides: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). It was found that FeO x −CoO x /TiO 2 showed the highest photocatalytic efficiency toward mineralization of selected herbicides. FeO x −CoO x /TiO 2 achieves 92% TOC removal in 180 min, representing nearly three time activity of the benchmark PC50 TiO 2 . From XPS analysis, FeOOH, CuO, and CoO were determined to be loaded onto the TiO 2 surface. The outstanding photocatalytic performance of the optimized FeO x −CoO x /TiO 2 sample for herbicides mineralization is due to an increased charge separation and enhanced hydroxyl radicals production monitored by diverse spectroscopies. Based on the proposed charge transfer mechanism, FeO x −CoO x cocatalyst species accelerate the transfer of photogenerated holes on TiO 2 , thus facilitating hydroxyl radicals production.

A Quantitative Study on the Effect of Fe Doping on the Surface-Available Photohole Concentration in TiO2 Nanoparticles

“…Typical Fe 2p XPS peaks located at around 710 and 722 eV were observed in 0.515%-Fe/TiO 2 samples (Figure C and Figure S4). The observed Fe 2p peaks could be fitted with six peaks, and two of them fitted at 709 and 722 eV could be assigned to Fe 3+ species, such as Fe 2 O 3 . ,, The peaks at 718 and 726 eV are also assigned to Fe 3+ species, which are the typical satellite peaks of Fe 3+ species. ,, The last two peaks at 713 and 724 eV could be related to the Fe­(OH) x species. ,, BET specific surface areas of TiO 2 and Fe/TiO 2 samples were measured to be 48.1 (TiO 2 ), 49.2 (0.056%-Fe/TiO 2 ), 48.5 (0.108%-Fe/TiO 2 ), and 51.1 (0.515%-Fe/TiO 2 ) m 2 /g. Thus, on the basis of the above comprehensive characterizations, it could be concluded that the Fe-doped TiO 2 nanoparticles were successfully synthesized.…”

“…The observed Fe 2p peaks could be fitted with six peaks, and two of them fitted at 709 and 722 eV could be assigned to Fe 3+ species, such as Fe 2 O 3 . 11,12,16 The peaks at 718 and 726 eV are also assigned to Fe 3+ species, which are the typical satellite peaks of Fe 3+ species. 11,12,16 The last two peaks at 713 and 724 eV could be related to the Fe(OH) x species.…”

“…11,12,16 The last two peaks at 713 and 724 eV could be related to the Fe(OH) x species. 11,12,16 BET specific surface areas of TiO 2 and Fe/ TiO 2 samples were measured to be 48.1 (TiO 2 ), 49.2 (0.056%-Fe/TiO 2 ), 48.5 (0.108%-Fe/TiO 2 ), and 51.1 (0.515%-Fe/ TiO 2 ) m 2 /g. Thus, on the basis of the above comprehensive characterizations, it could be concluded that the Fe-doped TiO 2 nanoparticles were successfully synthesized.…”

“…11,12,16 The peaks at 718 and 726 eV are also assigned to Fe 3+ species, which are the typical satellite peaks of Fe 3+ species. 11,12,16 The last two peaks at 713 and 724 eV could be related to the Fe(OH) x species. 11,12,16 BET specific surface areas of TiO 2 and Fe/ TiO 2 samples were measured to be 48.1 (TiO 2 ), 49.2 (0.056%-Fe/TiO 2 ), 48.5 (0.108%-Fe/TiO 2 ), and 51.1 (0.515%-Fe/ TiO 2 ) m 2 /g.…”

Cost-Effective and Highly Efficient Manganese-Doped MoS2 Nanosheets as Visible-Light-Driven Photocatalysts for Wastewater Treatment

“…In previous photocatalysis experiments, the UV spectrum was the main emphasis, and metal oxides like ZnO and TiO 2 were employed on a large scale as prominent catalysts. However, because UV light only makes up around 4–5% of the solar spectrum, this led to less efficiency. , Researchers are now tasked with engineering materials that maximize visible radiations to more than 50% efficiency for faster-photostimulated dye degradation. A promising method to increase the sensitivity of the photocatalyst for visible-light-driven dye degradation is to narrow the band gap by designing photocatalytic materials with a distinct band gap alignment.…”