This study systematically compares the visible‐light photocatalytic performance of coprecipitated divalent metal tungstate nanoparticles (MWO 4 ; M = Ni, Co, Zn, Cu) calcined at different temperatures. Characterization via X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and UV–vis spectroscopy revealed that calcination temperature critically controls crystallinity, phase purity, bandgap, and surface area. While higher temperatures enhanced crystallinity and caused a bandgap redshift, excessive sintering reduced surface area. NiWO 4 and CuWO 4 calcined at 550°C–650°C exhibited superior degradation of methylene blue, attributed to their optimal balance of reduced charge recombination, increased oxygen vacancies, and improved light absorption. This work demonstrates that the photocatalytic properties of tungstate nanocatalysts can be finely tuned through metal cation selection and controlled calcination.
Hossain et al. (Tue,) studied this question.