Increasing the photocatalytic efficiency of ZnWO4 by synthesizing a Bi2WO6/ZnWO4 composite photocatalyst

In the present study, a Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was successfully constructed by a modified hydrothermal synthesis method with different molar concentrations of Bi$_2$WO$_6$ with respect to ZnWO$_4$. The variation in molar concentrations of Bi$_2$WO$_6$ changed the photocatalytic properties of the Bi$_2$WO$_6$/ZnWO$_4$ catalyst. The synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was characterized by various techniques to decipher its structural and spectral properties. The interaction of Bi$^{2+}$ ionic charge carriers and many-body effects cause the band gap to narrow in Bi$_2$WO$_6$/ZnWO$_4$, as shown by PL analysis. The decrease in band gap energies (E$_g$) from 4.7 eV (ZnWO$_4$) to 3.5 eV (30% Bi$_2$WO$_6$/ZnWO$_4$) is beneficial because less energy is required to excite the valence electrons. The maximum degradation of Plasmocorinth B dye was found with 30% Bi$_2$WO$_6$/ZnWO$_4$ under UV irradiation. This increased activity of 30% Bi$_2$WO$_6$/ZnWO$_4$ can be attributed to the (i) synergistic effect in the bicrystalline framework of Bi$_2$WO$_6$ and ZnWO$_4$, (ii) the high close contact between Bi$_2$WO$_6$ and ZnWO$_4$, and (iii) the small crystallite size. The photocatalytic activity of synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst shows its significant potential in water/ wastewater treatment application.