Effect of surface modification and H2 reduction of WO3 nanoparticles in Methylene Blue photodegradation

We report the chemical synthesis of WO(3)nanoparticles, PtOx-WO3 nanoparticles and Pt-WO(3)nanoparticles with an average particle size of 20 nm. X-ray diffraction confirmed the formation of crystalline nanoparticles and the transmission electron microscope (TEM) images clearly show the presence of elemental Pt on WO(3)nanoparticles (NPs). Moreover, Energy Dispersive x-ray spectroscopy (EDX) and Raman spectroscopy confirm the presence of Pt on the surface of WO(3)NPs. The bandgap of WO3, PtOx-WO3 and Pt-WO3 was 2.78 eV, 2.59 eV and 2.28 eV respectively as determined by UV visible (UV-vis) spectroscopy. The H-2-Temperature Programme Reduction (TPR) of WO(3)and PtOx-WO(3)NPs confirms the increase in interaction of H(2)with PtOx-WO3 NPs. The photocatalytic performance of WO(3)NPs, PtOx-WO(3)NPs and Pt-WO(3)NPs was investigated for Methylene Blue (MB) degradation. Samples of PtOx-WO3 showed higher photocatalytic rate for MB degradation than WO(3)NPs. Importantly, a further increase in MB degradation efficiency was observed using Pt-WO(3)NPs photocatalyst. Apparent reaction rate constants 'kapp' for MB degradation, calculated from a Langmuir model are 0.003 0.001 min(-1), 0.018 0.003 min(-1)and 0.040 0.001 min(-1)for WO3, PtOx-WO(3)and Pt-WO(3)NPs photocatalyst respectively. The increase in the degradation performance was attributed to surface defects and surface generation of oxygen vacancies during H-2 reduction. The Pt-WO(3)NPs exhibited 94.7 0.6% Safranin-O (SO) degradation in 80 min and in this case the k(app) 0.027 +/- 0.001 min(-1).