Plasmonic gold nanoplates-decorated ZnO branched nanorods@TiO2 nanorods heterostructure photoanode for efficient photoelectrochemical water splitting.

[Display omitted] • Use ALD and hydrothermal method to attach ZnO branched nanorods to TiO 2 nanorod arrays on FTO substrate. • Incorporate Au triangular nanoplates (TNP) with ZnO@TiO 2 by immersing samples in Au TNP solution. • 3D ZnO provides more reactive sites, facilitates interfacial charge transfer and promotes efficient separation of photogenerated electron-hole pairs. • Surface plasmon resonance of Au TNP amplifies the local electromagnetic field and enhances light harvesting. • Improved photoelectrochemical properties of Au@ZnO@TiO 2 ternary heterostructure system are obtained. Transition metal-oxide semiconductors have shown great potential in the renewable energy harvesting and conversion, e.g., photoelectrochemical (PEC) water splitting. However, the existing disadvantages of semiconductors, such as insufficient solar light utilization and fast charge recombination, are urgently needed to be addressed to realize an efficient PEC device. In this work, we synthesized a well-defined ZnO branched nanorods (b-NRs) attached to TiO 2 nanorod (NR) arrays on FTO substrate using atomic layer deposition (ALD) and hydrothermal method. Meanwhile, Au triangular nanoplates (TNPs) were also incorporated with ZnO@TiO 2 heterostructure by immersing the structure in Au TNPs solution. The ZnO b-NRs@TiO 2 NRs and Au TNPs@ZnO b-NRs@TiO 2 NRs exhibited the photocurrent densities of 0.490 mA/cm2 and 0.733 mA/cm2 at 1.23 V vs. reversible hydrogen electrode which were 2.8 and 4.2 times of pure TiO 2 NR arrays (0.176 mA/cm2), respectively. Incident photon-to-current conversion efficiency measurements showed enhanced photoactivity after Au TNPs decoration. Moreover, the electrochemical impedance spectroscopy and Mott-Schottky analysis provided further evidence that the separation of photogenerated carriers and the transfer kinetics of charge carriers at the semiconductor/electrolyte interface were greatly improved by the ZnO b-NRs modification and Au TNPs decoration. It was concluded that the significantly enhanced PEC water splitting performance was attributed to the synergistic effect of the three-dimensional ZnO@TiO 2 composites heterostructure and the localized surface plasmon resonance resulting from Au TNPs. This study reported a facile combination of ALD and hydrothermal method for fabricating ZnO branched heterostructure and decorating Au TNPs to improve the PEC water splitting performance of TiO 2. [ABSTRACT FROM AUTHOR]