Promotional effect of Rh nanoparticles on WO3/TiO2 titanate nanotube photocatalysts for boosted hydrogen production

Abstract

"In this work, we explore the hydrogen production via the water splitting process on Rh-WO3 photocatalysts supported on nanotubes of TiO2. H2 production tests were performed in a 2-propanol-water solution. The support (titanate nanotubes, NT) was obtained, first, by the sol-gel method followed by the hydrothermal method. The surface of the titanate nanotubes was decorated with nanoparticles of rhodium and tungsten by applying microwave irradiation. The photocatalysts were characterized by XRD, HR-TEM, UV-vis, SBET, H2-TPR and XPS. For the photocatalytic tests, we employed two photocatalysts with 0.3 and 0.5 wt.% of Rh on WO3/TiO2 (3 wt.% of WO3) under UV-A light radiation at 365 nm and visible light at 450 nm. We found that 56 ?mol h?1 of hydrogen were produced by photolysis. The support (NT) produced 59 ?mol h?1 of hydrogen. The addition of 3 wt.% of WO3 to the nanotubes increased slightly the H2 production (66 ?mol h?1). However, a promotional effect was observed when rhodium was added to the 3WO3/NT photocatalysts. In fact, the highest hydrogen production was obtained on the 0.5Rh-3WO3/NT photocatalyst (234 ?mol h?1), even after seven cycles of 8 h. We suggest that Rh acts as co-catalyst of the WO3 during the water splitting process. A diagram for the density of states, based on the UV-vis and XPS results, is proposed."