Single-Crystalline Bi2YO4Cl with Facet-Aided Photocarrier Separation for Robust Solar Water Splitting

Bi2YO4Cl is a robust mixed-anion compound suitable for solar water splitting but generally delivers a mediocre catalytic level due to poor separation of photocarriers (e– and h+). In this work, we have modified Bi2YO4Cl by facet-engineering techniques, which generate plate-like single crystals dominantly exposing {001} and {100} crystal facets. These two sets of crystal facets are of diverse energy states, thereby setting up an internal built-in electric field that can readily separate and guide the flow of photocarriers. Thanks to this facet-aided charge separation mechanism, the faceted Bi2YO4Cl single crystals deliver much higher activities for solar water splitting reactions than conventional counterparts. Notably, the faceted Bi2YO4Cl single crystals can achieve apparent quantum efficiency as high as 7.51 and 2.52% at 420 ± 20 nm for photocatalytic O2- and H2-evolution from water, respectively. Stable overall water splitting under visible light illumination (λ ≥ 420 nm) has also been attained by merging the faceted Bi2YO4Cl single crystals into a Z-scheme system. As a photoanode material, the faceted Bi2YO4Cl single crystals can reach a high photocurrent density of ∼1.57 mA·cm–2 at 1.23 V vs RHE under AM 1.5G with a Faradic efficiency of almost unity.