PtOx-TiO2 anatase nanomaterials for photocatalytic reformation of methanol to hydrogen: effect of TiO2 morphology

Abstract

Pure TiO2 anatase semiconductor materials with three different morphologies (nanoparticles, nanotubes and nanofibers) were used to disperse with PtOx (2.0 wt.% nominal loading) nanoparticles. Structural, electronic and morphological characteristics of the calcined materials were studied by using XRD, Raman, DR UV–vis, XPS spectroscopy, transmission electron microscopy and N2 physisorption techniques. The band gap energy values were obtained from the Tauc plots and band gap energy values were decreased after deposition of PtOx over TiO2 nanomaterials. PtOx-TiO2 anatase nanotubes (2.0 Pt–Ti-A-NT) sample possessed unique physico-chemical properties such as high Pt dispersion, high surface area, pore volume and pore diameter in the range of 10–40 nm with unimodal distribution. The photocatalytic performances of all synthesized samples were tested for hydrogen production via reforming of aqueous methanol under visible light irradiation. To optimize the reaction conditions, several parameters such as methanol concentration, mass of the catalyst, pH of solution and reaction temperature were studied. Among the synthesized samples, 2.0PtOx-TiO2 anatase nanotubes sample exhibited highest photo activity for hydrogen generation. The observed results indicated the significant role of the morphology of TiO2 anatase semiconductor; decrease of the band gap energy, increasing electron storage and delayed electron–hole recombination due to high interaction between PtOx and TiO2 nanotubes. The highest performance for 2.0 PtOx-TiO2 anatase nanotubes sample at a promising hydrogen quantity of 1489 μmolg−1 was observed at 50 °C after 3 h.

Keywords

• Hydrogen
• Methanol
• PtOx-TiO2
• Morphology
• Nanoparticles
• Nanotubes