Study of Catalytic Activity of Graphitic Carbon Nitride in Photocatalytic Hydrogen Evolution: Comparison of Modification Approaches with One and Two Different Halogens

In this work, graphitic carbon nitride samples modified simultaneously with bromine and iodine were prepared using a two-step synthesis method. The composition and physicochemical properties of the prepared samples were investigated by a set of physicochemical methods including X-ray diffraction (XRD) analysis, low-temperature nitrogen adsorption, diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermal analysis, cyclic voltammetry, and impedance spectroscopy. The catalytic properties of the synthesized samples were measured under the illumination of an aqueous alkaline solution of triethanolamine. The samples simultaneously modified with bromine and iodine showed higher catalytic activity compared to the samples modified with bromine or iodine alone. A maximum catalytic activity of 2400 μmol h–1 g–1 was obtained in the presence of a 0.5% Pt/0.4Br–0.1I sample. Cyclic experiments showed that the samples modified with bromine or iodine alone showed higher photostability, as a result of which modification with one halogen allows the process of photocatalytic hydrogen evolution to be carried out with higher efficiency.