Elemental mercury removal by I−-doped Bi2WO6 with remarkable visible-light-driven photocatalytic oxidation

• Published in: Applied catalysis. B, Environmental Environmental, 2021-03, Vol.282, p.119534, Article 119534
• Main Authors: Zhang, Yili, Zhao, Yongchun, Xiong, Zhou, Gao, Tian, Gong, Bengen, Liu, Pengfei, Liu, Jing, Zhang, Junying
• Format: Article
• Language: English
• Subjects: Bismuth compounds; Carbon dioxide; Catalytic activity; Charge density; Charge transfer; Conduction bands; Density functional theory; DFT; Holes (electron deficiencies); Iodine; Irradiation; I– doped Bi2WO6; Light irradiation; Mercury; Mercury (metal); Oxidation; Photocatalysis; Photocatalytic Hg0 oxidation; Photooxidation; Potential energy; Radiation; Recombination; Sulfur dioxide; TPD; Tungstates; Visible light
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2020.119534

•Doping of I− into Bi2WO6 induced the lattice contraction of Bi2WO6 nanosheets.•doping decreased potential energy of CB edge, reserving good oxidation ability.•doped Bi2WO6 showed superior Hg0 photooxidation activity compared with Bi2WO6.•DFT calculations and mechanism for I− doped Bi2WO6 to oxidized Hg0 were elucidated. In this work, I–-doped Bi2WO6 composites were synthesized using a one-step hydrothermal method, and the effect of iodine doping on their photocatalytic efficiency in gas-phase elemental mercury removal was evaluated under visible-light irradiation. The results showed that 1.0 wt.% iodine doped Bi2WO6 exhibited the optimal Hg0 removal efficiency of 87.6 % and 97.5 % under N2+O2+CO2 and N2+O2+CO2+SO2+NO conditions, respectively. The improved photocatalytic activity of Bi2WO6 can be ascribed to the reduction in the potential energy of its conduction band and recombination rate of electron-hole pairs, as well as the acceleration of charge transfer. The density functional theory calculations showed that iodine was doped in the (WO4)2– layer and oxidized HgO can be adsorbed on the surface of I– doped Bi2WO6. The OBi site was found to be exhibit weak adsorption with respect to HgO, implying that most conducive to the desorption of HgO. Finally, the photocatalysis mechanisms was elaborated.