Photosensitivity of g-C3N4/S-doped carbon composites: study of surface stability upon exposure to CO2 and/or water in ambient light

Two series of materials based on graphitic carbon nitride (GCN) and sulfur-containing carbon (physical mixture and composite) were synthesized. The stability of their surface features upon exposure to either water, CO2 or to water and CO2 combined conditions in solar light was tested. Both materials generated photocurrent upon light exposure. The estimated band gap alignments indicate that although on both composite and physical mixture water splitting and CO2 reduction can take place in visible light, differences are expected in their extents. The results suggest that oxidation of water is more favorable on the composite while the physical mixture favors water and CO2 reduction, owing to the preserved s-triazine structure. While the surface of the former is oxidized by released oxygen, on the physical mixture material some degree of self-reduction is also noticed. The decrease in the porosity of the composite is linked to the oxidation of the carbon matrix.