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

Abstract

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.

Interlayer modification and single-layer exfoliation of the Ruddlesden–Popper perovskite oxynitride K2LaTa2O6N to improve photocatalytic H2 evolution activity

“…Recently, dye-sensitized niobate nanosheets and nanoscrolls have been reported to function as good H 2 evolution photocatalysts capable of functioning under visible light but the low stability of the dye component needs to be addressed. 14,44,45 In contrast to such dye-sensitized oxide systems, oxynitride nanosheets that are already capable of absorbing visible light do not require an additional photosensitizer dye. Thus, the results of this work demonstrate the signicant potential of twodimensional LaTa 2 O 6 N 2− sheets with regard to the construction of visible-light-driven water splitting systems.…”

A perspective on two pathways of photocatalytic water splitting and their practical application systems

“…Therefore, a significantly enhanced performance was reached by dual modification of the nanosheet photocatalyst with Al 2 O 3 and PSS. 101 Similar to one-step excitation OWS, conjugated polymer can also be used in Z-scheme systems. Tang's group constructed a visible-light-driven system by using PCN as the HEP.…”

Synthesis of the ZnTPyP/WO3nanorod-on-nanorod heterojunction direct Z-scheme with spatial charge separation ability for enhanced photocatalytic hydrogen generation

“…6–8 The photosynthesis-based Z-scheme photocatalytic system has recently been a cutting-edge research area due to the advantages of promoting the spatial separation of photogenerated charges to efficiently photoinduce water splitting into H 2 . 9–14…”

“…[6][7][8] The photosynthesis-based Z-scheme photocatalytic system has recently been a cutting-edge research area due to the advantages of promoting the spatial separation of photogenerated charges to efficiently photoinduce water splitting into H 2 . [9][10][11][12][13][14] To date, traditional solution Z-scheme photocatalysts with shuttle redox couples and all-solid-state Z-scheme photocata-lysts have been constructed and applied to solar H 2 generation. [15][16][17][18] However, the former are confined to the solution phase and need shuttle redox ion pairs to assist the transfer of photogenerated charge carriers, 19,20 while the latter are disadvantageous because their charge transfer relies on conductors.…”