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

TiO 2 nanotube-based heterostructures grafted with ZnO nanorods, Ag nanoparticles, or Pd nanodendrites were synthesized for photocatalytic H 2 O/CH 3 OH splitting and H 2 generation. Compared with P25 TiO 2 nanoparticles and bare TiO 2 nanotubes, these heterostructures, in particular, the one grafted with Pd nanodendrites, were found to present a markedly enhanced photocatalytic H 2 generation efficiency (net H 2 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 H 2 generation rate and the number of total photogenerated carriers was determined, which suggests that the number of effective carriers or the efficiency in H 2 O/CH 3 OH splitting might decay in an exponential way.