BiOCl ( = Ba, Sr, Ca) with Double and Triple Fluorite Layers for Visible-Light Water Splitting.

Layered oxyhalides containing double or triple fluorite layers are promising visible-light-responsive water-splitting photocatalysts with unique band structures. Herein, we report on the synthesis, structure, and photocatalytic property of BiBaOCl (4/) with alternating double (BiO) and triple (BiBaO) fluorite layers, which was extracted from the crystallographic database on the basis of Madelung potential calculations. Rietveld refinements from powder X-ray and neutron diffraction data revealed the presence of cationic disorder between BiO and BiBaO layers, leading to electrostatic stabilization. DFT calculations suggested that photogenerated electrons and holes flow through the double and triple layers, respectively, which may suppress electron-hole recombination. We expanded this double-triple system to include BiCaOCl and BiSrOCl with orthorhombic distortions and different degrees of cationic disorder, which allow band gap tuning. All the double-triple compounds BiOCl showed stable water-splitting photocatalysis in the presence of a sacrificial reagent.