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.

等离子体激元和光学模式（例如波导或谐振器模式）之间的强耦合会导致等离子体激元吸收带的分裂。结果，形成了表现出近场增强效果的两个新的混合模式。这些混合模式已经被利用来改善许多系统中的光吸收。在这里，我们证明了法布里-珀罗纳米腔模式与局部表面等离振子共振（LSPR）之间的这种模式强耦合促进了水分解反应。我们使用金纳米粒子（Au-NP）/ TiO ₂ / Au膜结构作为光阳极。该结构在TiO ₂的Fabry-Pérot纳米腔模式之间表现出模态强耦合。薄膜/金膜和金纳米粒子的LSPR。Au NPs的电子激发是通过跨多种波长的光学混合模式进行的，然后是热电子转移至TiO ₂。我们结构的关键特征是Au NPs部分镶嵌在TiO ₂层中，从而提高了耦合强度和水氧化效率。我们观察到，相对于没有Au膜的光阳极结构，入射光子到电流的转换效率提高了11倍。而且，在强耦合下，内部量子效率比未耦合条件下提高了1.5倍。