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

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 semi-conductors, 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 TiO2 nanorod (NR) arrays on FTO substrate using atomic layer deposition (ALD) and hy-drothermal method. Meanwhile, Au triangular nanoplates (TNPs) were also incorporated with ZnO@TiO2 het-erostructure by immersing the structure in Au TNPs solution. The ZnO b-NRs@TiO2 NRs and Au TNPs@ZnO b-NRs@TiO2 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 TiO2 NR arrays (0.176 mA/cm2), respectively. Incident photon-to-current conversion efficiency measurements showed enhanced photoactivity after Au TNPs decora-tion. Moreover, the electrochemical impedance spectroscopy and Mott-Schottky analysis provided further evi-dence 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 deco-ration. It was concluded that the significantly enhanced PEC water splitting performance was attributed to the synergistic effect of the three-dimensional ZnO@TiO2 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 TiO2.

Automated summary

This study synthesized well-defined ZnO branched nanorods and TiO2 nanorods on FTO substrate using atomic layer deposition and hydrothermal method, and incorporated Au triangular nanoplates with the ZnO@TiO2 heterostructure. The photocurrent densities of the ZnO b-NRs@TiO2 NRs and Au TNPs@ZnO b-NRs@TiO2 NRs were significantly higher than that of pure TiO2 NR arrays, and the photoactivity was enhanced after the decoration of Au TNPs.