Nitrogen Doping and Carbon Coating Affects Substrate Selectivity of TiO2 Photocatalytic Organic Pollutant Degradation

A series of carbon‐coated, nitrogen‐doped titanium dioxide photocatalysts was produced and characterized. N‐doped TiO2 powder samples were prepared using a sol‐gel method and subsequently used for making doped‐TiO2 thin films on glass substrates. Carbon layers were coated on the films by a thermal decomposition method using catechol. Diffuse reflectance spectra and Mott‐Schottky analyses of the samples proved that nitrogen doping and carbon coating can slightly lower the band gap of TiO2, broaden its absorption to visible light and enhance its n‐type character. According to photocatalytic tests against model contaminants, carbon‐coated nitrogen‐doped TiO2 films have better performance than simple TiO2 on the degradation of Rhodamine B dye molecules, but are poorly effective for degrading 4‐chlorophenol molecules. Several possible explanations are proposed for this result, supported by scavenging experiments. This reveals the importance of a broad substrate scope when assessing new photocatalytic materials for water treatment, something which is often overlooked in many literature studies.