Effects of Anionic Polymer Modification of Dye‐Sensitized Niobate Photocatalysts on Solar‐Driven Z‐Scheme Overall Water Splitting

Abstract

Pt‐intercalated calcium niobate nanosheets (Pt/HCa2Nb3O10) sensitized by a Ru(II) complex dye are good photocatalysts for producing H2 from aqueous solutions containing I− as a reversible electron donor. These materials are applicable to Z‐scheme overall water splitting in combination with a WO3‐based O2‐evolving photocatalyst under simulated sunlight. In this work, the effects of anionic polymer modification of the dye‐sensitized nanosheets are examined by adsorbing sodium poly(styrenesulfonate) (PSS), sodium polyacrylate, sodium polymethacrylate (PMA), or sodium poly(4‐styrenesulfonic‐co‐maleic acid) onto the dye‐sensitized nanosheet surface. For half‐cell H2‐evolution reaction in the presence of NaI, all of the polymers have a positive impact on the activity under visible light at lower light intensity, whereas only PMA is effective under high light‐intensity condition. For Z‐scheme overall water splitting with PtOx/H‐Cs‐WO3, PSS and PMA give almost the same solar‐to‐hydrogen energy conversion efficiencies (0.12% ± 0.01%) under optimized conditions. However, PMA operates better than PSS at relatively low and high NaI concentrations, which are in general disadvantageous for the H2‐ and O2‐evolving components of the Z‐scheme, respectively.