Surface photovoltage spectroscopy of carbon nitride powder

Powder of carbon nitride has been investigated by surface photovoltage spectroscopy at temperatures between 30 °C and 150 °C. Photo-generated holes were preferentially separated towards the external surface. Electronic states below the optical band gap from which charge separation may be possible have not been observed. The band gap of the investigated carbon nitride decreased from 2.93 to 2.80 eV with increasing temperature from 30 °C to 150 °C. The material exhibits a higher optical transition at E = 3.6 eV. Results are discussed from the point of view of photo-catalytic water splitting with carbon nitride.