Carbon, hydrogen adsorption-desorption

Hou, P.X., S.T. Xu, Z. Ying, Q.H. Yang, C. Liu, H.M. Cheng, Hydrogen adsorption/desorption behavior of multi-walled carbon nanotubes with different diameters. Carbon 41,2471-2476,2003. 

Palladium nanoparticles (nm-Pd) were synthesized by ship-in-a-bottle technique in supercages of NaA zeolite. The behaviors of electrodes of thin film of nm-Pd accommodated in NaA zeolite were characterized by cyclic voltammetry. The results illustrated that the nm-Pd possess particular properties for hydrogen reaction, i.e. in contrast to hydrogen absorption on massive palladium electrode, the surface processes of hydrogen adsorption-desorption become the dominant reaction on electrodes of thin film of nm-Pd. The processes of adsorption and desorption of carbon monoxide on the electrodes were studied using in situ electrochemical FTIR reflection spectroscopy. It has been revealed that in comparison with CO adsorbed on a massive Pd electrode, the IR absorption of CO adsorbed on nm-Pd particles accommodated in NaA zeolite has been enhanced to about 36 times. 

Figure 10.27. Hydrogen adsorption/desorption isotherms on super-activated carbon Anderson AX-21 with a BET surface area = 2800 m /g (see 10.4 on this carbon), soiid symbois = adsorption, open symbois = desorption (from Zhou and Zhou, 1998, with permission). (BET surface area from Benard and Chahine, 2001).

The electrochemical active surface area (EASA) of fuel cell Pt-based catalysts could be measured by the electrochemical hydrogen adsorption/desorption method. For carbon supported Pt, Pt alloy, and other noble metals catalysts, the real surface area can be measured by the cyclic voltammetry method [55-59], which is based on the formation of a hydrogen monolayer electrochemically adsorbed on the catalyst s surface. Generally, the electrode for measurement is prepared by dropping catalyst ink on the surface of smooth platinum or glassy carbon substrate (e.g, a glassy carbon disk electrode or platinum disk electrode), followed by drying to form a catalyst film on the substrate. The catalyst ink is composed of catalyst powder, adhesive material (e.g., Nafion solution), and solvent. 

Y. Kojima, Y. Kawai, A. Koiwai, N. Suzuki, T. Haga, T. Hioki, K. Tange, Hydrogen adsorption and desorption by carbon materials. J. Alloys Compd., 421 (2006) 204-208. 

The low-temperature physisorption (type I isotherm) of hydrogen in zeolites is in good agreement with the adsorption model mentioned above for nanostructured carbon. The desorption isotherm followed the same path as the adsorption, which indicates that no pore condensation occurred. The hydrogen adsorption in zeolites depends linearly on the specific surface areas of the materials and is in very good agreement with the results on carbon nanostructures [24]. 

Hydrogen storage in carbon has been considered during the last few years on account of the existence of new carbon nanomaterials, such as fullerenes, superactivated carbons, carbon monoliths, carbon nanotubes, and carbon nanohoms [147,166,176-179], distinguished by their high adsorption capacities, hydrophobic nature, and high adsorption/desorption rates [170],... 

Figure 6. Isotherms of hydrogen adsorption and desorption on carbon materials at temperature 77K, measured by the High Speed Gas Sorption Analyser NOVA 1200.

Dinitrophenylhydrazones (DNPHs) were applied to the GC analysis of keto acids. As with carbonyl compounds, they are prepared by reaction with 2,4-dinitrophenylhydrazine and are also used mainly for the preliminary isolation of keto acids. They can be isolated from a dilute aqueous sample by adsorption on activated carbon and selective desorption [178] hydrazones of aldehydes with a methyl formate-dichloromethane mixture and hydrazones of keto acids with a pyridine-water azeotropic mixture. Hydrazones of acids are released from their pyridine salts with methanol containing hydrogen chloride. After... 

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