Experimental and DFT insights into an eco-friendly photocatalytic system toward environmental remediation and hydrogen generation based on AgInS2 quantum dots embedded on Bi2WO6

Bismuth tungstate (Bi2WO6) can work as a photocatalyst but suffers from rapid recombination of photogenerated charge carriers. Herein, density functional theory (DFT) simulations revealed that the formation of a thermodynamically stable AgInS2(112)/Bi2WO6(010) heterojunction could promote charge separation and enhance the photoactivity of Bi2WO6. To confirm these theoretical predictions, a new type of photocatalysts in the form of Bi2WO6 flower-like microspheres decorated with different amounts of AgInS2 quantum dots (QDs) was obtained using a three-step procedure. The optimized system, obtained by embedding 1 wt% AgInS2 QDs on a Bi2WO6 matrix, possessed an enhanced photocatalytic activity for both phenol degradation and water splitting under visible light irradiation (λ > 420 nm), as well as good reusability and stability during prolonged storage. Finally, DFT calculations of the adsorption energies of reagents (O2, H2O, and H2 molecules) on Bi2WO6 and AgInS2/Bi2WO6 surfaces showed that the surface of the AgInS2(112)/Bi2WO6(010) interface was more active, allowing this system to strongly interact with surrounding species such as H2, O2, and H2O and thereby inducing photocatalytic oxidation of OH– to •OH, reduction of O2 to O2•– or reduction of H+ to H2.