TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis: the influence of N and Au doping

Abstract

The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO₂ materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO₂ nanoparticle supported catalyst demonstrated higher H₂O₂ selectivity and higher turnover frequency (TOF) than the catalysts based on TiO₂ nanowires. The addition of Au to the Pd TiO₂ nanowire catalyst improved the H₂O₂ selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H₂O₂ selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H₂O₂ as the primary product.