Study of Stuctural Formation of the Carbide Derived Carbon By X-Ray Microtomography and Small-Angle X-Ray Scattering Techniques
Authors: Härk Eneli , Petzold Albrecht , Goerigk Günter , Risse Sebastian , Ballauff Matthias , Schneider Sven , Hilger André , Kardjilov Nikolay , Tallo Indrek , Härmas Riinu , Lust Enn 
Published: February 2020

Depending on the synthesis route and conditions chosen, the carbons have different physico-chemical properties such as surface area, porosity, electronic and ionic conductivity, hydrophilicity and electrocatalytic activity [1-3]. Thus, for example the different binary metal carbide, selective chemical reaction of molecular halogen or HCl and temperatures of heat-treatment and H2 cleaning steps have a strong effect on the high surface area values with suitable pore shape, and pore size distribution of the synthesized carbon [3-5].

Similarly to other well-known carbide derived carbons (C(α-SiC, TiC, VC, WC)), the carbon synthesized from molybdenum carbide (Mo2C) has some advantages compared to various amorphous carbons such as high purity and narrow pore size distribution as well as low carbon degradation rate and high chemical stability at extreme potentials applied [3-5].

Due to the complexity of the morphology of the carbide derived carbon (CDC) pores and surfaces which contribute to the high capacitive or activity behaviour of the electrodes, there is still deficiency due date of the unambiguous correlation between the systematical structural features and electrochemical characteristics. Therefore, the main aim of this work was to ascertain the correlation between the structural formation and physical characteristics of CDC as a function of the synthesis temperature (from 600oC to 1000oC) [4]. The structural features obtained by small-angle X-ray scattering (SAXS) [6,7] and complementary studies with the X-ray microtomography (μCT) [7] have been conformed with other physical properties.

The μCT and SAXS measurements for five CDC samples synthesized at different chlorination temperatures (600, 700, 800, 900 or 1000oC) were conducted, and compared with commercially available RP-20 nanoporous carbon powder [6]. The linear attenuation coefficient values for various systems were estimated and phase densities of each CDC sample were calculated. The scattering curves in the high scattering vector range coincide for CDCs synthesized at 600, 700, 800 and 900oC, thought for CDC synthesised at 1000oC significantly deviates of those established for other nanoporous carbons, including for RP-20. Indicating directly to the extensive structural differences compared to other nanoporous carbons studied.

From application point of view, the most crucial structural features will be discussed in order to design the material with optimal micro- and mesopore fractions, which delivers the highest power at constant energy.

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