Enhanced water splitting under modal strong coupling conditions. Issue 10 (October 2018)

• Record Type: Journal Article
• Authors: Shi, Xu; Ueno, Kosei; Oshikiri, Tomoya; Sun, Quan; Sasaki, Keiji; Misawa, Hiroaki
• Is Part Of: Nature nanotechnology. Volume 13:Issue 10(2018:Oct.)
• Page Start: 953
• Page End: 958
• Publication Date: 2018-10
• Subjects: Nanotechnology -- Periodicals; 620.505
• DOI: 10.1038/s41565-018-0208-x
• Languages: English
• ISSNs: 1748-3387

Abstract

Abstract Strong coupling between plasmons and optical modes, such as waveguide or resonator modes, gives rise to a splitting in the plasmon absorption band. As a result, two new hybrid modes are formed that exhibit near-field enhancement effects. These hybrid modes have been exploited to improve light absorption in a number of systems. Here we show that this modal strong coupling between a Fabry–Pérot nanocavity mode and a localized surface plasmon resonance (LSPR) facilitates water splitting reactions. We use a gold nanoparticle (Au-NP)/TiO2 /Au-film structure as a photoanode. This structure exhibits modal strong coupling between the Fabry–Pérot nanocavity modes of the TiO2 thin film/Au film and LSPR of the Au NPs. Electronic excitation of the Au NPs is promoted by the optical hybrid modes across a broad range of wavelengths, followed by a hot electron transfer to TiO2 . A key feature of our structure is that the Au NPs are partially inlaid in the TiO2 layer, which results in an enhancement of the coupling strength and water-oxidation efficiency. We observe an 11-fold increase in the incident photon-to-current conversion efficiency with respect to a photoanode structure with no Au film. Also, the internal quantum efficiency is enhanced 1.5 times under a strong coupling over that under uncoupled conditions. Strong coupling between a Fabry–Pérot cavity mode and plasmonic modes enhances the internal quantum efficiency of a water splitting device.