An Artificial Z-Scheme Constructed from Dye-Sensitized Metal Oxide Nanosheets for Visible Light-Driven Overall Water Splitting

Abstract

Sensitization of a wide-gap oxide semiconductor with a visible-light-absorbing dye has been studied for decades as a means of producing H2 from water. However, efficient overall water splitting using a dye-sensitized oxide photocatalyst has remained an unmet challenge. Here we demonstrate visible-light-driven overall water splitting into H2 and O2 using HCa2Nb3O10 nanosheets sensitized by a Ru­(II) tris-diimine type photosensitizer, in combination with a WO3-based water oxidation photocatalyst and a triiodide/iodide redox couple. With the use of Pt-intercalated HCa2Nb3O10 nanosheets further modified with amorphous Al2O3 clusters as the H2 evolution component, the dye-based turnover number and frequency for H2 evolution reached 4580 and 1960 h–1, respectively. The apparent quantum yield for overall water splitting using 420 nm light was 2.4%, by far the highest among dye-sensitized overall water splitting systems reported to date. The present work clearly shows that a carefully designed dye/oxide hybrid has great potential for photocatalytic H2 production, and represents a significant leap forward in the development of solar-driven water splitting systems.

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt‐TiO2 Nanoparticles with a Double Layer of Photosensitizers

“…[28] Recently,M aeda and co-workers reported ah igh AQY value (2.4 %) for aZ -scheme DSPc omposedo fR u II dye-sensitized Al 2 O 3 /Pt/HCa 2 Nb 3 O 10 nanosheets for water reduction and aP tO x /H-Cs-WO 3 O 2 evolution photocatalyst. [39] These remarkablew orks suggestt hat suppression of the back reaction from the H 2 evolution Pt cocatalyst to the oxidizedr edox mediatorb yi mmobilizationo fP tc ocatalysti n the interlayer space of layered niobates is ak ey strategy for achieving electron donation from the redox mediator.H owever,t his approach does not improve the charges eparation efficiencyb etween the surface-immobilized PS and redox mediator.…”

“…reported overall water splitting (AQY=0.05 %) using coumarin derivatives (NKX‐2677) immobilized on Pt/H x K 4− x Nb 6 O 17 as a water reduction DSP coupled with an O 2 evolution photocatalyst comprising IrO 2 ‐Pt/WO 3 and iodide redox mediator [28] . Recently, Maeda and co‐workers reported a high AQY value (2.4 %) for a Z‐scheme DSP composed of Ru II dye‐sensitized Al 2 O 3 /Pt/HCa 2 Nb 3 O 10 nanosheets for water reduction and a PtO x /H‐Cs‐WO 3 O 2 evolution photocatalyst [39] . These remarkable works suggest that suppression of the back reaction from the H 2 evolution Pt cocatalyst to the oxidized redox mediator by immobilization of Pt cocatalyst in the interlayer space of layered niobates is a key strategy for achieving electron donation from the redox mediator.…”

Two‐Dimensional Transition Metal Oxides and Chalcogenides for Advanced Photocatalysis: Progress, Challenges, and Opportunities

“…Photocatalytic reactions mainly take place on the surface of catalysts where light is harvested, carriers are generated and transported, and reactant molecules are captured and transformed. Modifying the surface structure is the simplest way to modulate the catalytic activity of 2D TMOs and TMCs (e.g., MoS 2 /TiO 2 , [ 192 ] HCa 2 Nb 3 O 10 , [ 193 ] TiO 2 , [ 194 ] CdS [ 195 ] , ZnSe [ 196 ] ).…”

“…Lately, Oshima et al constructed a photocatalytic system for efficient water splitting under visible light using HCa 2 Nb 3 O 10 NSs sensitized by a Ru(II) tris‐diimine type photosensitizer. [ 193 ] Because the visible light sensitizer, [Ru(4,4′‐(CH 3 ) 2 ‐bpy) 2 (4,4′‐(PO 3 H 2 ) 2 ‐bpy)] 2+ (bpy=2,2′‐bipryridine) (denoted as RuP), has a negative oxidation potential when it is oxidized, electrons can be injected into the CB of HCa 2 Nb 3 O 10 NSs (Figure 23b). Intriguingly, the thin HCa 2 Nb 3 O 10 NSs are notably advantageous in accommodating the sensitizer, as the maximum amount of RuP adsorbed on NSs is about five times higher than that on the layered bulk counterpart.…”

Significantly Raised Visible‐Light Photocatalytic H2 Evolution on a 2D/2D ReS2/In2ZnS4 van der Waals Heterostructure

“…Photocatalytic water splitting converts abundant sunlight into storable/carbon‐free H 2 . [ 1–43 ] Thus, it has attracted significant research attention. Of particular importance is the rational design of highly‐efficient, stable and inexpensive photocatalysts.…”