Single-Source Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides

Bismuth oxyhalides are a promising class of photocatalystsforharvesting solar energy. These materials are often synthesized inaqueous media with poor synthetic control resulting from the extremelyfast nucleation and growth rates of the particles. These fast ratesare caused by the rapid precipitation of bismuth salts with free halideions. We have developed water-soluble precursors combining bismuthwith either chlorine or bromine atoms in the same metal-organiccomplex. With the application of heat, halide ions are released, whichthen precipitate with bismuth ions as BiOX (X = Cl, Br). By controllingthe halide ion formation rate, the nucleation and growth rates ofBiOX materials can be tuned to provide synthetic control. The diversepotential of these precursors is demonstrated by synthesizing BiOXin three ways: aqueous colloidal synthesis, solid-state decomposition,and fabrication of films of BiOX via spray pyrolysis of the aqueousprecursor solutions. These broadly applicable single-source precursorswill enhance the ability to synthesize future BiOX materials withcontrolled morphologies. Controlledbismuth oxyhalide synthesis in water is challengingdue to fast nucleation and growth rates caused by poor solubility.Water-soluble precursors with bismuth and halogen atoms in the samecomplex were created to control halide ion formation, which reducesthe nucleation and growth rates for better control of BiOX nanomaterialsynthesis.