Improved photocatalytic activity of Y-doped WO₃ in reduction of Cu(II) in industrial effluent

The synthesis of tungsten trioxide (WO₃) and (1, 3 and 5% m/m) yttrium-doped tungsten trioxide (Y–WO₃) was achieved using hydrothermal method. The structural and optical properties of the synthesized material were characterized using XRD, TEM, FESEM, BET, DRS, FTIR, PL and Raman. The monoclinic polymorphs were attained as confirmed by the XRD, FTIR and Raman analysis, whose rectangular shapes were observed through FESEM. The doping of the materials was visually observed via the HRTEM imagery; the d-spacing was altered (by an increase of 0.0069 nm) on doping with yttrium ions. Doping of the materials also resulted in lowered band gaps corresponding to shifted valence band and conduction band. The metal doping also influenced a positive shift of the point of zero charge to higher pH, recording the highest point of zero charge at 3.43 pH. The effect of doping on recombination of carrier charges was investigated using PL analysis. These observations were attributed by the influence of Y orbital on the band gap region of WO₃ as supported by the DFT calculations. The photoactivity of the material was evaluated using the reduction of Cu(II) ion in wastewater (working pH 6.05), where a photoreduction of 98% was achieved in 60 min.