Importance of Electron Mediator Transparency: Photocatalytic Hydrogen Production from Polyoxometalate using Dye‐double‐layered Photocatalysts

Abstract

AbstractOne‐directional electron transfer is crucial for two‐step photoexcitation (Z‐scheme) water‐splitting photocatalysis. We investigated the hydrogen evolution activity of PS‐double‐layered photocatalysts (X‐DSP, X‐RuCP6‐Zr‐RuP6@Pt/KxH4‐xNb6O17; X=Zr4+, H+) in the presence of highly charged polyoxometalates‐K6[SiVIVW11O40] ⋅ nH2O (VIV‐POM) and K6[SiW11O39MnII(H2O)] ⋅ nH2O (MnII‐POM)‐as redox‐reversible electron donors, to induce effective photocatalyst‐donor electrostatic attraction. Surface‐phosphonate‐comprising H+‐DSP completely one‐electron oxidized VIV‐POM with 0.39 % apparent quantum yield in the initial hour (iAQY) in both HCl and phosphate buffer aqueous solutions. Conversely, the Zr4+‐DSP iAQY decreased to 0.05 % in HCl aq. Considering that the 0.39 % iAQY was retained when replacing VIV‐POM with MnII‐POM in HCl aq, we supposed that energy transfer deactivation from photoexcited PS* to surface‐immobilized VIV‐POM is the plausible origin of the lower iAQY, owing to the stronger visible‐light absorptivity of VIV‐POM. This suggests that accumulation of visible‐light‐transparent electron mediator on the photocatalyst surface is an effective approach for one‐directional electron transfer in Z‐scheme water‐splitting photocatalysis.