Efficient Hot‐Electron Transfer under Modal Strong Coupling Conditions with Sacrificial Electron Donors

Abstract In this study, we investigated the hot‐electron transfer efficiency under modal strong coupling conditions by monitoring the photocurrent generated at a plasmonic photoanode. We fabricated a gold nanoparticles/titanium dioxide/gold film structure that shows a modal strong coupling between the Fabry−Pérot nanocavity mode and the localized surface plasmon and then explored the effect of the strong coupling on the incident photon‐to‐current conversion efficiency (IPCE) and internal quantum efficiency (IQE) in the presence of triethanolamine (TEOA) as a sacrificial electron donor to accelerate the surface reaction enough. The IPCEs for the upper and lower branches of the strong coupling were enhanced up to 4.5 and 4.0 times, respectively, by the addition of TEOA. Additionally, the average IQE with TEOA at wavelengths from 500 to 800 nm reached 3%. The Fermi level shifts due to the generation and consumption of hot‐carriers were also discussed by comparing the in situ spectroelectrochemical measurements with and without TEOA.