Improved water splitting efficiency of Au-NP-loaded Ga2O3 thin films in the visible region under strong coupling conditions

Abstract

We fabricate a novel photoanode consisting of TiO₂/Au nanoparticles (Au-NPs)/Ga₂O₃/TiN/Au-film (TAGA), efficiently increasing light absorption and electron transfer from Au-NPs to Ga₂O₃ under modal strong coupling. A TiN thin layer deposited on an Au film enables stable high-temperature deposition of Ga₂O₃ onto the reflective Au film mirror. Modal strong coupling is observed when the resonance wavelength of the Ga₂O₃/TiN/Au-film Fabry–Pérot cavity overlaps with the plasmon resonance wavelength of Au-NPs partially inlaid in a thin TiO₂ layer. Under strong coupling conditions, the light absorption and photoelectrochemical conversion efficiency in the visible region increased more than in the samples without coupling. In this structure, the TiO₂ layer partially inlaying Au-NPs plays a vital role in effectively enhancing the coupling strength. We accomplish water splitting at zero bias potential by taking advantage of the intrinsically negative conduction band potential of Ga₂O₃.