Enhanced photoactivity in nitrogen-doped KM0.33W1.67O6 (M = Al and Cr)

The investigation of photocatalysis by efficient visible-light-active photocatalysts has been of interest in both the science and the engineering fields. The nitrogen (N) doped KAl_0.33W_1.67O₆ (KAW) and KCr_0.33W_1.67O₆ (KCW) are prepared by the solid state method. Urea was used as a nitrogen source. These materials were characterised by thermo gravimetric analysis, powder X-ray diffraction, scanning electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). Both the N-doped materials crystallised in a cubic lattice with space group Fd3̅m. The XPS analysis of the N-doped KAW (N-doped KCW) show the characteristic peaks belonging to K 2p, Al 2p (Cr 2p), W 4f, O 1s and N 1s along with C 1s. The bandgap energy was deduced from their UV-vis DRS profiles. The photocatalytic degradation of the methylene blue solution was investigated in the presence of these oxides. Compared with their parent materials, nitrogen doped KAW and KCW samples exhibit ~230 and ~130% increase, respectively, in visible light-induced photodegradation of methylene blue.