Why the quantum chemical models of active carbons, which were obtained by the ‘technology following’ methodology are so differ from the commonly accepted graphite-like model?
The commonly accepted model for the activated carbon structure is flat graphite fragment, may be with defect(s), and terminated by the hydrogen atoms and/or functional groups. Therefore, the point of view of masters in active carbon chemistry is [Activated Carbon; Harry Marsh and Francisco Rodríguez-Reinoso; Copyright © 2006 Elsevier Ltd.]: Question: Can activated carbons be described as amorphous materials? Answer. Emphatically, no.
No comments to this. But, the vibration spectra of graphite and active carbon (type SKS from synthetic polymer or other), obtained by inelastic neutron method (where no selected rules are work and one can see amplitude weighted density of vibration states – AWDS) are greatly differ! It means that the structures of these two carbon’s form are greatly differing too! The physical properties, which can be tested very easy and directly – hardness – for these two carbon’s form are greatly differ too! Graphite has hardness near 1 by Moos scale and some samples of the SKS active carbon can scratch the hardening steel! Graphite cannot do this! We simulate the carbonization process using next methodology. Step-by-step we remove that groups (hydrogen and hydroxyl, if they are presented) from the starting molecule(s), which produces the gases from carbonization process (hydrogen and water, if it is possible, molecules). After that, the system under study is optimized and process repeats again up to complete carbonization. One of the obtained structures is shown here. The main differences between our model and commonly accepted graphite-like model are: 1. We have cycle size distribution. It means that we have 3-fold, 4- fold, 5- fold, 6- fold, 7- fold,8- fold and more folds cycles in comparable amount, while the graphite-like model only now can accept a small amount 5-fold and seven-fold cycles into graphene plane – the most important renovation into graphite-like model during last 70 years. 2. We have a big amount of two-fold coordinated carbon atoms in the carben-carbin-coumulet chains. Nobody from carbon-coal chemists would like to accept this idea! 3. A lot of benzene cycles have a triple bond. And again nobody from carbon-coal chemists would like to accept this idea! As I know from my discussions with that scientists, nobody know the term ‘Aryne Chemistry’ and the article: “One Century of Aryne Chemistry” by Hans Henning Wenk, Dr., Michael Winkler, Dipl.-Chem., Wolfram Sander, Prof. Dr. – Angewandte Chemie International Edition, 2003, v. 42, No 5, p. 502-528. My question to them: “What should be with graphene plane, which terminated by hydrogen atoms, after mechanical partition onto two parts?”. Every times I had got the answere: “the dangling bonds”! What is means “ the dangling bonds ”? – “ The bonds after breaking-off!” – “How many “the dangling bonds” one can obtain after removing two hydrogen from ethane CH3-CH3 (one hydrogen per one carbons)? - Qualify chemists usually say: “No dangling bonds – one has got the ethylene H2C=CH2”. Illiterate chemists and most physicist usually say: “ Two dangling bonds”!!! How to improve the brains?
But the question about active carbon structure for the time being is opened! Where is the exact model? A big amount of the cycle size distribution and two-fold coordinated carbon atoms are the quantum chemistry deviation from the true? Or it is the deviation of the ‘technology following’ methodology? Or it is unknown and unidentified mistake? Or, the most probable, we have the same structure, but we look on it from the different sides? (те же яйца, только в профиль!)??? May be, the common send on the active carbon was formed at that old time, when only graphite and diamond were known. Starting from the black color and common physical properties (electric conductivity) and some XRD data (but XRD cannot directly define the amorphous part!) only graphite-like model was proposed at the times of Rosalind E.Franklin [Rosalind E.Franklin. - Crystallite growth in graphitizing and non-graphitizing carbons. - Proc. R. Soc. Lond. Ser. A, 1951, v. 209, p. 196-218] and nobody whould like to improve these types of models? Only small corrections to this graphite-like model as 5-fold and 7-fold cycles as rare defects in regular 6-fold cycles. For chemists were introduced the functional groups to describe the chemical properties of the active carbons. As usually, physicists would not like to take in account these “chemical impurities”. As result – lack of common model to describe and predict the properties of different carbon materials. But, our experience in the silica glass structure simulation shows that any amount of defects, introduced into crystal structure, cannot convert it into amorphous silica glass structure. Last data [J. -F. Poggemann, G. Heide, G. H. Frischat. - Direct view of the structure of different glass fracture surfaces by atomic force microscopy - Journal of Non-Crystalline Solids, 2003, v. 326-327, p. 15-20 and others] about direct observation on the silica glass structure has supported our amorphous model [V Khavryutchenko, J Garapon, B Poumellec. - Structure simulation of silica glasses: approach to CVD - Modelling Simul. Mater. Sci. Eng., 2001, v. 9, p. 465-483]. Who can solve this very interesting situation?