We hypothesized that photocatalysts with a low band gap could be useful in the sterilization of ceramic tiles in the natural environments of toilets using natural light in those settings. Certain photocatalysts can produce reactive oxygen species (ROS) under light illumination, which in turn are bactericidal. The properties of the BiOBr-containing photocatalysts were tuned by creating junctions and heterostructures with Ag and InVO₄ and studied with respect to their bactericidal effect in dispersion. The bactericidal mechanism was studied through experiments in which active species were captured and via electron paramagnetic resonance (EPR) spectroscopy. At an optimal dosage of 0.5 g/L, the Ag/InVO₄/BiOBr composite had a sterilization efficacy of 99.9999 % in 30 min under visible light illumination of 1000 W. It retained a sterilization efficacy of 99.999 % after four cycles. Anions such as Cl⁻, SO₄²⁻, and NO₃⁻ were shown to have no negative impact on sterilization efficacy. It was shown that the holes in the composite photocatalyst and hydroxyl radicals (·OH) were mechanistically critical for the sterilization. The photocatalysts were also studied in the field in the natural environment of a restroom, where they were loaded on ceramic tiles. Samples were collected from the surface of the ceramic tiles and analyzed for bacterial cultures and microbial diversity. The results were compared in the scope of the sterilization ability of various agents at the microbial level. The ceramic tiles loaded with Ag/InVO₄/BiOBr showed the least amount of bacteria on their surfaces, and the microbial community richness was also the lowest.