Plasmonic gold (Au) nanostructures are great attractive for visible-light-driven water splitting due to their excellent chemical stability and strong visible light absorption via localized surface plasmon resonance (LSPR). The absorbed light in the Au nanostructures can be converted to hot carriers via the decay of LSP that can be subsequently utilized for photocatalytic water splitting. Here we introduce a plasmonic photoanode comprising three-dimensional (3D) porous network of colloidal gold nanoparticles (AuNPs) coupled with an oxygen evolving catalyst. The 3D Au nanostructured photoanode is prepared by the layer-by-layer (LbL) assembly of negatively charged AuNPs and cationic polyethyleneimine (PEI) on a titanium oxide (TiO2) thin layer. First, the hot carrier transfer in the photoanodes is investigated depending on the interfacial properties under visible light illumination. The photocurrents increase with the removal of the PEI layer by calcination because the PEI layer prevents the hot carrier transfer from AuNPs to TiO2. The multi-layered assembly varies the structural and optical properties of the Au nanostructures that are associated with the generation and injection of hot carriers. The unique 3D porous networks of the multi-layered Au nanostructures are retained during thermal annealing with a silica layer that is removed by a 30 % KOH solution, which absorb a broadband solar spectrum from visible to NIR region. Furthermore, IrO2 hydrosols are assembled on the multi-layered Au nanostructures as water oxidation catalysts. Plasmonic photocurrents significantly increase with the increased number of AuNP layers under visible light illumination. The results indicate that the hot carrier generation in the Au due to the SPR increases with the enhanced light absorption. Our study suggests that the optimized plasmonic nanostructures based on AuNPs will provide a promising light-harvesting platform for sustainable and efficient solar water splitting in the visible region.

Three dimensionally assembled gold nanostructures for visible light-driven water oxidation

253rd National Meeting (2017)

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