Solvothermal synthesis of pure and Sn-doped BiS and the evaluation of their photocatalytic activity on the degradation of methylene blue.

Background: A large volume of dye molecules finds its way into the environment, accumulates in water bodies, and makes the aquatic system unsafe to human health. Due to the complex nature of these dye materials, most of the conventional techniques are not effective for their removal. Semiconductor photocatalysis has emerged as a promising technique for  the destruction of organic pollutants under UV or visible light irradiation. Among the semiconductors, BiS is widely employed in photocatalysis due to its non-toxicity and chemical stability. However, one of its problems is the high recombination rate of the charge, and various methods have been employed to enhance the photo-reactivity. One of  these methods is the incorporation of transition elements.

Results: Herein, a facile solvothermal method was used to prepare BiS nanorods and needle- shaped Sn doped BiS, using bismuth(III) tris(N-phenyldithiocarbamate) as a single-source precursor. The prepared nanomaterials were characterized, and used as efficient photocatalyst for the photo enhanced degradation of methylene blue (MB) dye under visible light irradiation. The nanomaterials exhibited very good photocatalytic activity towards the photo degradation of MB, showing a degradation rate of up to 83% and 94% within 150 min for the pristine and Sn doped BiS,  respectively.

Conclusion: The enhancement in the photocatalytic activity of the Sn doped BiS was attributed to the suppression in the recombination rate of the electron-hole pairs, due to the formation of new energy level below the CB, that was capable of altering the equilibrium concentration of the carrier. This confirmed that Sn doped BiS could be utilized as valuable cost-efficient catalysts for eliminating methyl blue from aqueous solutions and also possible candidates in environmental pollution treatment.