Synthesis of efficient photocatalysts for water oxidation and dye degradation reactions using CoCl2 eutectics

A simple one-step procedure for the preparation of cobalt oxide-carbon nitride composites by carrying out the thermal condensation reaction of carbon nitride precursors in cobalt(II) chloride-containing salt melts is developed. This method enables us to control the structure of the polymer constituent by the proper selection of the second eutectic component. In this respect, alkali metal chlorides and zinc chloride give rise to poly(triazine imides), while tin(II) chloride delivers melon-based polymers. The crystallinity of the carbon nitride polymer phase can be influenced by varying the concentration of the precursor in the melt. On the other hand, cobalt oxide loading in the final products can be increased by decreasing the precursor concentration in the melt. The products are highly active photocatalysts for Rhodamine B degradation as exemplified by SnCl2/CoCl2-derived solids, and the water oxidation reaction (WOR). The activity of the products in the WOR is comparable with that of the bench composite photocatalyst prepared by using the three-step procedure that includes the synthesis of Co3O4 nanoparticles as a separate step, thus illustrating the advantages of the developed salt melt assisted approach.