Broad spectrum photocatalytic system based on BiVO4 and NaYbF4:Tm3+ upconversion particles for environmental remediation under UV-vis-NIR illumination

The development of photocatalysts responsive towards a broader region of the solar (UV-to-NIR) light is important for efficient harvesting of sunlight for photochemical and photoelectrical applications. In this study, two photocatalytic systems (BV/LEDs and BV/UCPs where UCPs stands for NaYbF4:Tm3+ upconversion particles) based on bismuth vanadate (BV) are introduced for photocatalytic degradation of both organic dyes (crystal violet, CV) and pharmaceuticals (sulfathiazole, STZ) under a variety of photoactivation modes including low-power (1.26 W) LEDs and near infrared (NIR) irradiation as well as natural sunlight. The BV/LEDs system makes use of the perfect match between the emission profile of commercial blue LEDs (460 +/- 10 nm) and absorption profile of BV (E-g = 2.6 eV) to effectively photodegrade pollutants. The BV/UCPs system, on the other hand, exploits the NIR-to-UV/visible upconverted light from UCPs to allow photodegradation of pollutants under NIR illumination. Moreover, we present a detailed study of the experimental parameters to obtain BV particles with tailored morphology (spherical, rod-like, hyperbranched), crystalline phase (monoclinic, tetragonal or heterojunction biphasic BV) and band gap energy (2.4-2.9 eV). Depending on the phase composition, a synergetic effect in photoactivity is observed in samples containing around 68% monoclinic and 30% tetragonal BV which is ascribed to the formation of monoclinic/tetragonal heterojunction.