Elucidating the layered structure of the g-C ₃ N ₄ nanomaterials using X-ray photoelectron spectroscopy and X-ray powder diffraction techniques is possible.

Graphitic carbon nitride (g-C₃N₄) was obtained by thermal polymerization of dicyandiamide, thiourea or melamine at high temperatures (550 and 600 °C), using different heating rates (2 or 10 °C min⁻¹) and synthesis times (0 or 4 h). The effects of the synthesis conditions and type of the precursor on the efficiency of g-C₃N₄ were studied. The most efficient was the synthesis from dicyandiamide, 53%, while the efficiency in the process of synthesis from melamine and thiourea were much smaller, 26% and 11%, respectively. On the basis of the results provided by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), thermogravimetric analysis (TGA), elemental analysis (EA), the best precursor and the optimum conditions of synthesis of g-C₃N₄ were identified to get the product of the most stable structure, the highest degree of ordering and condensation of structure and finally the highest photocatalytic activity. It was found that as the proton concentration decreased and the degree of condensation increased, the hydrogen yields during the photocatalytic decomposition of water–methanol solution were significantly enhanced. The generation of hydrogen was 1200 µmol g⁻¹ and the selectivity towards hydrogen of more than 98%.

Selective catalytic reduction of halogenated nitroaromatic compounds is the most widely used method for the synthesis of halogenated anilines, important intermediates in the chemistry of pesticides, herbicides, drugs, pigments and dyes. This review reports progress made in the last decade in the field of hydrogenation of halogenated nitro arenes with the use of heterogeneous catalysts. The first sections of the review contain a concise report on applications of halogenated anilines, methods for their preparation and reaction pathways for hydrogenation of haloaromatic nitro compounds. Subsequent sections discuss hydrogenation properties of platinum group metals, new catalysts based on gold and silver as well as nickel catalysts. Particular attention is paid to positive effects of the use of new unconventional supports and catalyst preparation methods. Finally, an attempt is made at systematising the most important factors affecting high activity and selectivity of heterogeneous catalysts for selective reduction of haloaromatic nitro compounds.