Synthesis of bulk and nanoporous carbon nitride polymers from ammonium thiocyanate for photocatalytic hydrogen evolution

Abstract

Graphitic carbon nitride was synthesized by direct thermal polymerization of ammonium thiocyanate as the precursor. The transfer of this simple thermal-induced polymerization onto hard-templates with various nanoarchitectures enables the fabrication of nanostructured carbon nitridesvia a soft-chemical synthesis, while the involvement of a sulfur species within the reaction cascade offers additional chemical control of the texture and the electronic structures. The catalysts were subjected to several characterizations, and the results obtained revealed that nanoporous carbon nitrides can be obtained by templating with nanosized silica and SBA-15. Photocatalytic activity was evaluated toward hydrogen evolution from proton solution with visible light. Results show that g-C₃N₄ synthesized from ammonium thiocyanate exhibited improved photoactivity in comparison with g-C₃N₄ obtained from dicyandiamide. Further improvement in the activity was achieved by creating the nanostructures in g-C₃N₄. This is due to the enhanced surface area obtained which is favorable for light-harvesting and mass-transfer, as well as to the increased redox potential.