g-C3N4/In2O3 heterojunction films and their excellent photocatalytic performance in fruit preservation and organic dye degradation

We prepared g-C3N4/In2O3 composite films on the wire mesh of stainless steel by a hydrothermal method combined with annealing. XRD, SEM, and XPS results confirmed the heterojunction formation of g-C3N4/In2O3. UV-vis spectroscopy showed that the heterojunction films exhibited enhanced visible light absorption capacity compared with the pristine In2O3 films. Compared with the individual In2O3 films, the PL intensity of the g-C3N4/In2O3 composite films was remarkably reduced, their photocurrent density was significantly increased, and the semicircle in EIS plots was reduced. All the above changes are attributed to the heterojunction formation between g-C3N4 and In2O3. According to our proposed mechanism, photogenerated electrons transfer from g-C3N4 to In2O3 while the holes move in the opposite direction. Therefore, the spatial transfer and separation of photoinduced electrons and holes was achieved. In other words, the recombination efficiency of photogenerated electrons and holes was remarkably suppressed. In photocatalytic RhB degradation, g-C3N4/In2O3 heterojunction films exhibited much higher photocatalytic activity than the pristine In2O3 films. In our self-made photocatalytic fruit-preservation system, these g-C3N4/In2O3 heterojunction films showed excellent fruit preservation ability. Specifically, the bananas remained turquoise green without turning yellow or black spots, even black patches, after a seven-day evaluation period.