Water oxidation of visible-light-responsive bismuth-yttrium oxychloride promoted by a dual-ion doping strategy for assembly of Z-scheme overall water splitting

Bismuth yttrium oxychloride (Bi 2 YO 4 Cl) is one of the most popular visible-light-responsive photocatalysts; however, it is still challenging to use it in the construction of overall water splitting (OWS) systems. Herein, we introduce a novel dual-ion doping strategy to modulate its structure and water oxidation activity, based on which a feasible Z-scheme OWS system can be assembled. In particular, the doping effect of dual ions (Y 3+ and Br − ) on the structure and water splitting performance was examined and discussed by combining various characterization studies such as photoelectrochemical current, electrochemical impedance spectroscopy, (time-resolved) photoluminescence spectra, and density functional theory calculations. It was observed that a clear synergistic promotion effect occurs on the dual ion-doped sample (Bi 3− x Y x O 4 Cl 1− y Br y ), making it exhibit a significantly higher O 2 evolution rate compared to a single ion-doped sample. The activity was also observed to strongly depend on the content of dual ions, and the optimized Bi 1.2 Y 1.8 O 4 Cl 0.88 Br 0.12 sample exhibited a remarkable visible-light-responsive O 2 production rate of 116 μmol h −1 (the apparent quantum efficiency (AQE) = 5.4% at 420 nm), which was 10 and 20 times higher than those of the Br-/Y-doped sample and pristine Bi 2 YO 4 Cl, respectively. The substantially promoted charge separation and reduced activation energy were demonstrated to be responsible for the excellent O 2 -evolution rate. Finally, we successfully fabricated a feasible Z-scheme OWS system based on the colorless IO 3 − /I − shuttle redox pair by employing modified Bi 1.2 Y 1.8 O 4 Cl 0.88 Br 0.12 as the O 2 -evolving photocatalyst along with ZrO 2 /TaON as the H 2 -evolving photocatalyst. The dual-ion doping strategy may be extended to several other photocatalysts for enhanced photocatalytic activities. A novel dual ion doping strategy to modulate the structure of Bi 2 YO 4 Cl is introduced and the first successful visible-light-responsive oxyhalide-based Z-scheme OWS system based on the colorless IO 3 − /I − shuttle redox pair is fabricated.