ZnO/Ag/Ag₂WO₄ photo-electrodes with plasmonic behavior for enhanced photoelectrochemical water oxidation

Ag-based compounds are excellent co-catalyst that can enhance harvesting visible light and increase photo-generated charge carrier separation owing to its surface plasmon resonance (SPR) effect in photoelectrochemical (PEC) applications. However, the PEC performance of a ZnO/Ag/Ag₂WO₄ heterostructure with SPR behavior has not been fully studied so far. Here we report the preparation of a ZnO/Ag/Ag₂WO₄ photo-electrode with SPR behavior by a low temperature hydrothermal chemical growth method followed by a successive ionic layer adsorption and reaction (SILAR) method. The properties of the prepared samples were investigated by different characterization techniques, which confirm that Ag/Ag₂WO₄ was deposited on the ZnO NRs. The Ag₂WO₄/Ag/ZnO photo-electrode showed an enhancement in PEC performance compared to bare ZnO NRs. The observed enhancement is attributed to the red shift of the optical absorption spectrum of the Ag₂WO₄/Ag/ZnO to the visible region (>400 nm) and to the SPR effect of surface metallic silver (Ag⁰) particles from the Ag/Ag₂WO₄ that could generate electron-hole pairs under illumination of low energy visible sun light. Finally, we proposed the PEC mechanism of the Ag₂WO₄/Ag/ZnO photo-electrode with an energy band structure and possible electron-hole separation and transportation in the ZnO/Ag/Ag₂WO₄ heterostructure with SPR effect for water oxidation.