High-pressure synthesis of sp(2)-bonded carbon nitrides

We have synthesized amorphous sp(2)-bonded carbon nitrides at high pressure. A precursor composed of carbon and nitrogen, tetracyanoethylene, was compressed in a diamond anvil cell and laser heated to approximately 2000 degrees C. Transmission electron microscopy, electron diffraction, electron energy loss spectroscopy, and energy-dispersive X-ray analysis have been used to characterize the structure, bonding, and composition of the carbon nitrides. The amount of nitrogen incorporated into the network increases with pressure, ranging from 24% (C3N) at 18 GPa to 38% at 42 GPa (C3N1.9), which represents the most nitrogen-rich carbon nitride yet prepared under pressure. A crystalline carbon phase is also found.