Surface-modified, dye-sensitized niobate nanosheets enabling an efficient solar-driven Z-scheme for overall water splitting

While dye-sensitized metal oxides are good candidates as H(2) evolution photocatalysts for solar-driven Z-scheme water splitting, their solar-to-hydrogen (STH) energy conversion efficiencies remain low because of uncontrolled charge recombination reactions. Here, we show that modification of Ru dye–sensitized, Pt-intercalated HCa(2)Nb(3)O(10) nanosheets (Ru/Pt/HCa(2)Nb(3)O(10)) with both amorphous Al(2)O(3) and poly(styrenesulfonate) (PSS) improves the STH efficiency of Z-scheme overall water splitting by a factor of ~100, when the nanosheets are used in combination with a WO(3)-based O(2) evolution photocatalyst and an I(3)(−)/I(−) redox mediator, relative to an analogous system that uses unmodified Ru/Pt/HCa(2)Nb(3)O(10). By using the optimized photocatalyst, PSS/Ru/Al(2)O(3)/Pt/HCa(2)Nb(3)O(10), a maximum STH of 0.12% and an apparent quantum yield of 4.1% at 420 nm were obtained, by far the highest among dye-sensitized water splitting systems and comparable to conventional semiconductor-based suspended particulate photocatalyst systems.