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

Bismuth oxyhalides are a promising class of photocatalysts for harvesting solar energy. These materials are often synthesized in aqueous media with poor synthetic control resulting from the extremely fast nucleation and growth rates of the particles. These fast rates are caused by the rapid precipitation of bismuth salts with free halide ions. We have developed water-soluble precursors combining bismuth with either chlorine or bromine atoms in the same metal-organic complex. With the application of heat, halide ions are released, which then precipitate with bismuth ions as BiOX (X = Cl, Br). By controlling the halide ion formation rate, the nucleation and growth rates of BiOX materials can be tuned to provide synthetic control. The diverse potential of these precursors is demonstrated by synthesizing BiOX in three ways: aqueous colloidal synthesis, solid-state decomposition, and fabrication of films of BiOX via spray pyrolysis of the aqueous precursor solutions. These broadly applicable single-source precursors will enhance the ability to synthesize future BiOX materials with controlled morphologies.