First fluorine doping of In2O3 films and its crucial role in enhancing photocatalytic activity.

• Fluorine-doped In 2 O 3 film was prepared for the first time. • The doping decreased the bandgap and recombination of photogenerated carriers. • The doping promoted the formation of a porous morphology, enhancing dye adsorption. • The doping increased the photocatalytic activity of the In 2 O 3 film by 7.6 times. We prepared In 2 O 3 film on the wire mesh of stainless steel by a facile hydrothermal method followed by annealing. To enhance the visible-light-responsive photocatalytic activity of the prepared In 2 O 3 film, we in-situ doped the element fluorine by adding FTO glass as the fluorine source during the hydrothermal process. The prepared In 2 O 3 and F-doped In 2 O 3 films were characterized by XRD, SEM, HRTEM, XPS, UV–vis spectra, PL, and electrochemical measurement. The results show that In 2 O 3 octagonal pyramids of cubic phase were formed. The fluorine doping promoted to growth of In 2 O 3 pyramids and porous In 2 O 3 pyramids help to adsorb RhB dye molecules. Beside, the fluorine doping introduced a new impurity level between the VB and CB of In 2 O 3 , thereby, decreasing the bandgap value from 2.84 to 2.60 eV. As a result, it extended the visible light absorption range and more photoinduced electrons and holes can be excited under simulated sunlight. Moreover, the doping inhibited the recombination of photogenerated carriers. It is worth noting that the fluorine doping changed the surface state of In 2 O 3 and enhanced the chemical adsorption of dissociated oxygen species. It finally made RhB dye molecules strongly adsorbed the surface of F-doped In 2 O 3 film. The photocatalytic activity of the F-doped In 2 O 3 film was increased by 7.6 times compared with the pristine In 2 O 3 film because of the combined action of the above reasons. The importance of active groups for RhB photodegradation is O 2 • − > h+ > e− > • OH. [Display omitted] [ABSTRACT FROM AUTHOR]