Self-assembly synthesis of monodisperse BiVO₄ nanosphere via a hybrid strategy for photoelectrochemical water splitting

Monodisperse semiconductor sphere holds great potential for a wide variety of application as a basic building block. Herein a binary oxide, BiVO₄, with highly uniform monodisperse nanosphere of 125 nm diameter was primarily synthesized via a hybrid method with PVP assisted in organic solvent. After investigating the function of PVP and the emergence of esterification in solvent, we proposed a formation mechanism of amorphous BiVO₄ nanosphere, including the precipitation of BiVO₄ clusters in reverse micelles and the self-assembly aggregation of BiVO₄ clusters to be BiVO₄ nanospheres. The generated water in esterification provides a nanoreactor to precipitate BiVO₄ cluster, in return, the precipitation by using water catalyzes the process of esterification in ethanol with acetic acid. This hybrid reaction of inorganic BiVO₄ precipitate and organic esterification opens a novel avenue to couple nano inorganic chemistry with organic dehydration synthesis, achieving green chemistry for sustainable development. Furthermore, highly efficient nanoporous BiVO₄ photoanodes composed of BiVO₄ nanospheres for water splitting were obtained using a simple drop-casting method and optimized for their photocurrent density by calcination temperatures. This hybrid reaction strategy could be applied to synthesize other semiconductors with nanosphere toward novel low-cost structures and devices.