Tuning the redox potential of Ag@Ag2O/WO3 and Ag@Ag2S/WO3 photocatalysts toward diclofenac oxidation and nitrophenol reduction

Abstract

WO3 nanoplates modified with either Ag2O or Ag2S nano-architectures were synthesized by a deposition-hydrothermal route (180 °C for 5 h). They were characterized using X-ray powder diffraction, N2 sorptiometry, Transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photo-catalytic (λ > 420 nm, 160 W) degradation of Diclofenac (DCF; 60 mg/l), was achieved using H2O2 (1 × 10−4 M) with either Ag@Ag2O/WO3 (K = 32.0 × 10-3 min-1) or Ag@Ag2S/WO3 (K = 7.3 × 10-3 min-1) catalysts. In the case of DCF degradation using radical scavengers, O2− played a key role in the degradation process whilst OH and holes acted moderately minor roles. The possible DCF degradation paths and intermediates were assessed by LC–MS. Both Ag@Ag2O/WO3 and Ag@Ag2S/WO3 catalysts were used in the photo-reduction of 4-nitrophenol (4-NP; 1.8 × 10−4 M) to 4-aminophenol (4-AP) with rate constants equal 8.3 x 10−3 min-1 and 1.6 x 10−3 min−1, respectively.