Photocatalytic H2 Generation Efficiencies of TiO2 Nanotube-based Heterostructures Grafted with ZnO Nanorods, Ag Nanoparticles, or Pd Nanodendrites

Abstract

TiO2 nanotube-based heterostructures grafted with ZnO nanorods, Ag nanoparticles, or Pd nanodendrites were synthesized for photocatalytic H2O/CH3OH splitting and H2 generation. Compared with P25 TiO2 nanoparticles and bare TiO2 nanotubes, these heterostructures, in particular, the one grafted with Pd nanodendrites, were found to present a markedly enhanced photocatalytic H2 generation efficiency (net H2 generation rate ∼143 μmol/h). Rather than the surface area of the photocatalysts, the lifetime (separation) of photogenerated carriers and, in particular, the surface plasmon resonance-stimulated carrier excitation dominated the number of total effective carriers. A power relationship with an exponent of 0.2 between the H2 generation rate and the number of total photogenerated carriers was determined, which suggests that the number of effective carriers or the efficiency in H2O/CH3OH splitting might decay in an exponential way.