Visible-LEDs-induced photocatalytic activity of Bi2WO6/BiVO4 heterojunctions prepared by a novel and green methodology

Photocatalytic activity can be boosted by coupling semiconductors, promoting well-aligned potential bands, narrowing energy gaps (Eg), and enhancing the separation of photogenerated carriers. Bi2WO6/BiVO4 (BiW/BiV) heterojunctions with different contents of BiW were successfully prepared by a metathesis-assisted molten salts route. This route has several outstanding features such as novelty, green chemistry, high yield, efficiency, use of simple equipment, and intermediate temperature. In the as-synthesized heterojunctions, the BiW content influenced the catalytic activity. Silver nanoparticles (Ag-NPs) and graphene (G) were loaded to the 1BiW/1BiV (wt/wt) heterojunction, affecting physicochemical characteristics and photocatalytic performance. The BiW/BiV heterojunctions were composed of plate and spherical-like nanoparticles of BiV and BiW, respectively. The junction zone of BiV and BiW and their high crystallinity were confirmed, as well as the contact between Ag and BiW. The percentage of rhodamine B (RhB) degradation (%XRhB) over Ag/1BiW/1BiV reached 100% within 210 min under 19 W power blue LEDs irradiation. Here, the power consumption against %XRhB achieved via LEDs illumination and using Ag/1BiW/1BiV heterojunction was superior to the literature reports using Xe and Hg lamps. Besides, the RhB degradation depends on the initial dye concentration, catalyst dosage, and the solution pH. The primary oxidative species inducing the RhB degradation were h+ and ·O2− determined by scavenger tests, and the carrier transfer mechanism in Ag/1BiW/1BiV was postulated. After four reuse cycles, the Ag/1BiW/1BiV catalyst exhibited high chemical stability.