Improved photocatalytic activity of Bi2MoO6 by modifying the halogen ions (Cl−, Br−, or I−) for photoreduction of N2 into NH3

A series of halogen ions (Cl − , Br − , or I − ) modified Bi 2 MoO 6 (Bi 2 MoO 6 –Cl, Bi 2 MoO 6 –Br, or Bi 2 MoO 6 –I) are synthesized via a one-step solvothermal method. It is determined that the halogen ions (Cl − , Br − , or I − ) are modified on the surface of Bi 2 MoO 6 as the -Bi-Cl, -Bi-Br, or -Bi-I species (the connected Bi 3+ is coordinated with three lattice O2- ions in Bi 2 MoO 6 ). The -Bi-Cl, -Bi-Br, or -Bi-I species on the Bi 2 MoO 6 surface can act as highly active sites to polarize and activate the N 2 and H 2 O molecules adsorbed on the surface of catalysts. Moreover, due to the surface-modified -Bi-Cl, -Bi-Br, or -Bi-I species, the visible light absorption is improved, the separation of photogenerated charge carriers is promoted, as well the band structure is better matched with the redox potential of photoreduction of N 2 . As a result, the photocatalytic activity of Bi 2 MoO 6 –Cl, Bi 2 MoO 6 –Br, or Bi 2 MoO 6 –I is improved for photoreduction of N 2 into NH 3 compared with Bi 2 MoO 6 . Overall, this work provides new insights into the doping states of halogen ions, the surface-active sites, the band structure, the photocatalytic activity, and the mechanism for photoreduction of N 2 into NH 3 for Bi 2 MoO 6 with modification of halogen ions (Cl − , Br − , or I − ). Schematic of photocatalytic mechanism of Bi 2 MoO 6 , Bi 2 MoO 6 –Cl 3%, Bi 2 MoO 6 –Br 3%, and Bi 2 MoO 6 –I 3%. • The halogen ions (Cl − , Br − , or I − ) are modified on surface of Bi 2 MoO 6 as species. • The surface halogen species as active sites can promote surface adsorption ability. • The energy levels of halogen species can regulate the band structure. • The surface halogen species can promote the separation of photo-generated carriers. • The surface halogen species can improve photocatalytic activity.