Single-Crystalline Bi<sub>2</sub>YO<sub>4</sub>Cl with Facet-Aided Photocarrier Separation for Robust Solar Water Splitting
Jinxing Yu, Shufang Chang, Li Shi, Xiaoxiang Xu
Abstract
Bi 2 YO 4 Cl 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 Bi 2 YO 4 Cl 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 Bi 2 YO 4 Cl single crystals deliver much higher activities for solar water splitting reactions than conventional counterparts. Notably, the faceted Bi 2 YO 4 Cl single crystals can achieve apparent quantum efficiency as high as 7.51 and 2.52% at 420 ± 20 nm for photocatalytic O 2 - and H 2 -evolution from water, respectively. Stable overall water splitting under visible light illumination (λ ≥ 420 nm) has also been attained by merging the faceted Bi 2 YO 4 Cl single crystals into a Z-scheme system. As a photoanode material, the faceted Bi 2 YO 4 Cl 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.