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

Abstract We report the chemical synthesis of WO 3 nanoparticles, PtO x –WO 3 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 WO 3 , PtO x –WO 3 and Pt–WO 3 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 PtO x –WO 3 NPs confirms the increase in interaction of H 2 with PtO x –WO 3 NPs. The photocatalytic performance of WO 3 NPs, PtO x –WO 3 NPs and Pt–WO 3 NPs was investigated for Methylene Blue (MB) degradation. Samples of PtO x –WO 3 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 WO 3 , PtO x –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 a p p 0.027 ± 0.001 min −1 .