Direct Evidence of an Efficient Plasmon-Induced Hot-Electron Transfer at an in Situ Grown Ag/TiO₂ Interface for Highly Enhanced Solar H₂ Generation

Plasmon-induced hot-electron generation and its efficient transfer to the conduction band (CB) of neighboring metal oxides is an effective route to solar energy harvesting. However, until now, this process has been very inefficient due to the poor charge transfer rate from plasmonic metal nanoparticles (NPs) to the CB of the oxide semiconductor. In this work, an in situ grown synthesis method has been developed to grow plasmonic Ag NPs within a titanium oxide (TiO₂) matrix. This synthesis method allows us to deposit Ag NPs surrounded by a TiO₂ semiconductor, which results in an efficient charge transfer from the Ag NPs to the CB of TiO₂ and has been utilized for highly enhanced electro-photocatalytic H₂ generation. Photoelectrochemical measurement of optimized Ag(NPs)-TiO₂ thin film photoanodes showed a high photocurrent generation at a density of 42 mA cm^-2 in 1 M KOH solution, which is three orders of magnitude higher than that of pure TiO₂, and stability for more than 1.5 h. These data indicates that it has excellent potential application for photoelectrochemical (PEC) water splitting. An intense photocurrent generation in the region of plasmonic absorption of Ag NPs with a peak position of 435 nm has been observed; this photocurrent generation reveals direct evidence of a strong contribution of plasmon-induced hot electrons for solar energy conversion.