Sonochemical synthesis of large two-dimensional Bi2O2CO3 nanosheets for hydrogen evolution in photocatalytic water splitting.

Laterally large (~3 micrometers), atomically-thin two-dimensional (2D) Bi2O2CO3 nanosheets (2D bismuth oxycarbonate, 2D bismutite) are fabricated via sonochemically-assisted template-free synthesis. Key to the synthesis of the freestanding, laterally large 2D Bi2O2CO3 nanosheets from bulk Bi powder is choice of suspension medium, controlled reaction temperatures and several hours processing time. Lateral sizes of 2D Bi2O2CO3 can be controlled between micrometer-sized nanosheets and tens of nm sized nanoflakes solely based on the choice of suspension medium. The here introduced 2D Bi2O2CO3 nanosheets/-flakes are then hybridized by a simple mix-and-match approach with TiO2 nanoparticles for testing in suspension-type photocatalytic hydrogen production via water splitting. This introduces the 2D Bi2O2CO3 with TiO2 as a promising noble-metal-free co-catalyst for photocatalytic hydrogen evolution. Our results enrich the fabrication toolbox of emerging 2D pnictogen oxycarbonates towards large 2D nanosheets and demonstrate the promising potential of 2D Bi2O2CO3 as an advantageous (co-)catalyst for hydrogen evolution in photocatalytic water splitting.