Enhancing H₂ evolution and molecular oxygen activation via dye sensitized BiOBr_0.9I_0.1 under visible light

Sensitization with a dye has great potential for dealing with the photoexcited charge recombination problem for photocatalysts. One of the main factors affecting the dye-sensitization performance is the absorption capacity of semiconductor for dye. Specific surface area of semiconductors and pH values of reaction system are critical for the absorption capacity. Herein, we firstly developed a BiOBr_0.9I_0.1 solid solution via a facile and fast sacrificial template method. The prepared BiOBr_0.9I_0.1 has distinct advantages, e.g. loose and rich porous structure, more oxygen vacancies (OVs), and a large specific surface area, which result in strong adsorption for dye molecules. Sensitized by Rhodamine B (RhB), the prepared BiOBr_0.9I_0.1 photocatalyst shows remarkably improved high activity for H₂ evolution, which is 27.9 times than that of the dense structured BiOBr_0.9I_0.1 under a direct photocatalytic process. By lowing the pH of RhB solution, the absorption ability is further improved because of the protonation of dye. At low pH, the prepared BiOBr_0.9I_0.1 can efficiently activate the molecular oxygen to produce superoxide radicals (O₂^-), resulting a super high dye-sensitized degradation activity for tetracycline hydrochloride (TCH) and methyl orange (MO) pollutants, outperforming most catalysts reported under similar conditions by the direct photocatalytic reaction. The present method represents a new direction in the development of dye-sensitization nanomaterials with good performance for energy and environment applications.