  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.
