Boehm’s method

The surface chemical properties of the carbon materials were characterized as follows measurement of pH of carbon slurries (in 0.1 M NaCl solution) [89] neutralization with bases of different strength and dilute HCl according to Boehm s method [63,66] determination of total oxygen/nitrogen content by elemental analysis (with an accuracy of 0.2%) [170] mass loss of carbon samples after heat treatment in a vacuum. Additionally, the number of primary adsorption centers (a,)) was determined from water vapor adsorption isotherms according to the Dubinin-Serpinsky method [171], as was the heat of immersion in water for selected samples [111,172]. The results of these operations are pre.sented in Table 3. For all samples transmission Fourier Transform Infrared (FTIR) spectra and X-ray photoelectron spectra (XPS) were recorded. 

SI = Sibunit (activated pyrolytic carbon), A = Anthralur (active carbon). Subscript ox means oxidized support (with the oxidant indicated in the brackets) HT the support calcined in inert atmosphere at 1000 °C. Determined from Na2C03, NaOH, NaOEt, and HCl consumption in accordance with Boehm s method. Source Ref. 16. 

Table 24.7 Characteristics of activated carbon after an oxidation reaction, Gi are the surface functional groups determined by Boehm s method, Gi for carboxylic acid, G2 for lactone, G3 for phenol, and G4 for carbonyl. These groups are differentiated by neutralization with solutions (0.05N) of NaHCOj, Na COj, NaOH, and CH CH ONa [50]. 100 g of activated carbon in 500 ml of water with or without an oxidant...

Information about textural and substructural characteristics of the supports (surface area, micropore volume, crystallographic data) was derived from nitrogen and phenol adsorption data measurements, wide angle X-ray scattering (WAXS) spectra and high resolution electron microscopy (HREM). Concentrations of the surface oxides were determined using the data on the adsorption of NagCOs, NaOH, NaOEt and HCl in accordance with Boehm s method [3]. 

It is seen that the ZCP is strongly dependent on acid treatment. The results of titration by using Boehm s method are also given in Table 5.5. The untreated sample of this particular activated carbon (North American carbon, low ash , <2%) is basic, with ZCP = 10. Carboxyl is the most abundant group on aU acid treated carbons. The approximate distribution of different add groups is seen from the titration results. 

The pH of MCM-41 was measured with ASTM D 3838. About l.Og of dry MCM-41 was added to 20 ml of distilled water, and the suspension was shaken overnight to reach equilibrium. Then the sample was filtered, and pH of the solution was measured. The surface functional groups of the samples were determined by Boehm s titration method [13]. In the case of acid value, about l.Og of the sample was added to 100 ml of O.IN NaOH solution and the mixture was shaken for 24 h. Then the solution was filtered through a membrane filter and titrated with 0. IN HCI. Likewise, the base value was determined by converse titration. 

Thirdly, in order to improve the dispersion of platinum catalysts deposited on carbon materials, the effects of surface plasma treatment of carbon blacks (CBs) were investigated. The surface characteristics of the CBs were determined by fourier transformed-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and Boehm s titration method. The electrochemical properties of the plasma-treated CBs-supported Pt (Pt/CBs) catalysts were analyzed by linear sweep voltammetry (LSV) experiments. From the results of FT-IR and acid-base values, N2-plasma treatment of the CBs at 300 W intensity led to a formation of a free radical on the CBs. The peak intensity increased with increase of the treatment time, due to the formation of new basic functional groups (such as C-N, C=N, -NHs, -NH, and =NH) by the free radical on the CBs. Accordingly, the basic values were enhanced by the basic functional groups. However, after a specific reaction time, Nz-plasma treatment could hardly influence on change of the surface functional groups of CBs, due to the disappearance of free radical. Consequently, it was found that optimal treatment time was 30 second for the best electro activity of Pt/CBs catalysts and the N2-plasma treated Pt/CBs possessed the better electrochemical properties than the pristine Pt/CBs. 

Boehm s titration This method was used to evaluate the amount of carboxylic acid, lactone and phenol groups present at the surface of caibon samples, by stirring 0.5 g of carbon in 50 mL of NaHCOs, Na2C03 or NaOH [2]. The carbon was filtered out after 24 h and the filtrate was titrated with hydrochloric acid. All solutions were prepared using freshly distilled decarbonated water and maintained under nitrogen. 

---