Optimizing electronic structure through lattice engineering for enhanced photocatalytic reduction of Cr(VI)

In this work, a nanorod-like K+ doped ZnWO4 photocatalyst was synthesized via a straightforward hydrothermal method assisted by potassium nitrate etching. The optimized K-ZnWO4 exhibits excellent photocatalytic activity for Cr(VI) reduction, with a high removal rate (92.6 %), fast kinetic constant (7.33 x 10-3 min-1 ), and good cycle stability (over 90 % removal rate sustained for 5 cycles). The physicochemical properties of the synthesized samples were thoroughly characterized using XRD, N2 physical adsorption, TEM, FT-IR, UV-vis DRS, XPS, TPR, and EIS. Structural characterizations revealed that the introduction of K+ reduces the sample size and increases surface roughness, facilitating the transformation from ZnWO4 nanoblocks to K-ZnWO4 nanorods. Notably, K+ doping induces lattice expansion in ZnWO4, leading to an increased electron cloud density near Zn active sites. The optimized d-band center accelerates the kinetics of Cr(VI) reduction, thereby enhancing the photocatalytic activities. This work provides deeper insight into how lattice defects optimize the electronic structure to enhance the Cr(VI) removal performance of tungstate photocatalysts.