Surface-Plasmon-Resonance-Enhanced Photoelectrochemical Water Splitting from Au-Nanoparticle-Decorated 3D TiO₂ Nanorod Architectures

Surface plasmonic resonance (SPR) is a new paradigm in photoelectrochemical (PEC) research that realizes the persistent supply of green energy in a sustainable manner. However, typical approaches for decorating surfaces Au nanoparticles (NPs), such as the colloidal chemical method, nanolithography, and in situ photo/thermal reduction, involve multiple complex steps and often introduce unwanted surface/interface chemicals that jeopardize the SPR effect and charge transport. Herein, we report a largely enhanced PEC performance achieved by decorating Au NPs onto 3D titanium dioxide (TiO 2 ) nanorod architectures grown by surface-reaction-limited pulsed chemical vapor deposition through a one-step sputtering process. The Au NP size and amount could be manipulated in a controlled manner. Compared to pristine TiO 2, the Au–TiO 2 electrodes achieved high photocurrent density enhancements of 42% and 267% under simulated sunlight and visible-light illumination, respectively. When amorphous aluminum oxide (Al 2 O 3 ) films were applied to the Au–TiO 2 photoelectrodes, the PEC performance was further increased by 87.8%. Moreover, three-dimensional (3D) finite-difference time-domain simulations were employed to investigate the spatial distribution of electric-field intensity around the Au NPs in different cases. The PEC enhancement was confirmed to follow the localized electromagnetic enhancement and hot-electron-injection mechanism upon SPR excitation. This facile and effective Au-NP decoration approach makes it possible to design plasmonic metal/semiconductor structures for other general photoanode improvements.