Abstract
Plasmonic nanostructures show great promise in enhancing the solar water splitting efficiency due to their ability to confine light to extremely small volumes inside semiconductors. While size plays a critical role in the plasmonic performance of Au nanoparticles (AuNPs), its influence on plasmon-assisted water splitting is still not fully understood. This holds especially true for low band gap semiconductors, for which interband excitations occur in wavelength regions that overlap with plasmonic resonances. Here, BiVO4 films are modified with AuNPs of diameters varying from 10 to 80 nm to study the size dependence of the plasmonic effect. Plasmon resonance energy transfer (PRET) is found to be the dominant effect in enhancing the water splitting efficiency of BiVO4. “Hot electron” injection effect is weak in the case of BiVO4/AuNP. This is attributed to the interband excitation of BiVO4, which is unfavourable for the hot electrons accumulation in BiVO4 conduction band. The resonant scattering effect also contributes to the enhanced water splitting efficiency for the larger diameter AuNPs. It is also for the first time found that higher PRET effect can be achieved at larger off-normal irradiation angle.
Highlights
Anticipated that higher solar-to-H2 energy conversion efficiency can be achieved if one can confine and manipulate light absorption in the first and second regions of the semiconductor
BiVO4 films combined with AuNPs with diameters varying from 10 to 80 nm are investigated as photoanodes for PEC water splitting
We observe that the plasmonic field confinement and water splitting efficiency of BiVO4/AuNPs sensitively depends on the particle size of the AuNPs
Summary
Anticipated that higher solar-to-H2 energy conversion efficiency can be achieved if one can confine and manipulate light absorption in the first and second regions of the semiconductor. We observe that the plasmonic field confinement and water splitting efficiency of BiVO4/AuNPs sensitively depends on the particle size of the AuNPs. Maximum enhancement is found for AuNPs with a diameter of 30 nm due to a pronounced overlap of the resonantly amplified electric near-field with the interband excitation in BiVO4.
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