Physico-Chemical nanomaterials science
Сobalt-nitrogen-contained nanocatalysts
Anastasiia Ruda, Iryna Ivanenko
Department of Inorganic Substances Technology, Water Treatment and General Chemical Engineering of National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", 4 building, 37 Pеremohy ave., 03056, Kyiv, Ukraine
E-mail Address: irinaivanenko@hotmail.com

Based on Norit SAE SUPER industrial powdered activated carbon, a preparative batch of samples was synthesized: oxidized, oxidized cobalt-contained, nitrogen-contained, and nitrogen-cobalt-contained activated carbon.
The specific surface area (excluding the original activated carbon) is the highest in oxidized activated carbon (640 m2/g); it decreases almost twice after its nitriding (320-350 m2/g). Cobalt modification has little effect on Ssp. Samples of nitrided cobalt-containing activated carbon have the smallest specific surface area. Interestingly, that their as Ssp decrease as Co content increases; in our opinion, due to the filling of the internal volume of micro- and mesopores during deposition of Cobalt particles. The corresponding trend is maintained for the total pore volume of the synthesized samples.
X-ray phase analysis proved the presence of the Co phase in the composition of the synthesized samples, the number, and intensity of their peaks increase with the increasing Co content. The original and oxidized activated carbon is X-ray amorphous, and the addition of a nitrogen-containing component of different nature (melamine and urea) makes them more structured.
Thermal analysis showed that the presence of nitrogen in active carbon increases the thermal stability of the samples in comparison with non-nitrided. For non-nitrided samples, a smooth mass loss is observed, with almost the entire mass of the samples subjected to thermal destruction up to 550 ºC. The thermograms of nitrided samples clearly distinguish two areas of active mass loss of the material: up to 410 ºC surface functional groups burn (~10%), and the bulk of the material (~70%) is subjected to thermal destruction in the temperature range from 410 to 650 ºC. That is, nitrided cobalt-containing activated carbon withstands the load and loses half of its mass at higher temperatures, and therefore such samples can work stably up to 410 ºC.
It was found that the pH of the synthesized samples` surface varies depending on the processing method. The highest pH value of the surface (10.1) belongs to the oxidized cobalt-containing sample. The active carbon treated only with nitric acid shows the lowest pH value (4.7). The pH of nitrided samples were close to neutral, and pH of the surface of nitrided cobalt-containing samples increases with the addition of cobalt (7.8) and does not depend on its amount in the samples.