Plasmonic Au nanoparticles on 8 nm TiO₂ nanotubes for enhanced photocatalytic water splitting

We report here for the first time a successful distribution and attachment of fine Au nanoparticles on ∼8 nm diameter TiO₂ nanotubes having significantly increased surface area. Au thin film deposition onto hydrothermally grown TiO₂ nanotube arrays followed by thermal annealing breaks up the Au film into desired, uniformly distributed nanoparticles. Visible light absorption spectra of the gold nanoparticles on TiO₂ nanotubes indicate that the Au nanoparticles are photo-excited due to plasmon resonance, and charge separation is accomplished by the transfer of photoexcited electrons from the gold particle to the TiO₂ conduction band, thereby enhancing photoelectrochemical performance. By virtue of substantially increased surface area with the 8 nm TiO₂ nanotube substrate in combination with the plasmonic effect of distributed Au nanoparticles, significantly increased photocurrent density was obtained with extended light absorbance from the UV regime to the visible spectrum region. Such gold nanoparticle decorated, fine TiO₂ nanostructures fabricated by a simple and versatile method can be useful for hydrogen generation by water splitting, CO oxidation and various other types of photocatalysts and photovoltaic fuel cells.