Carbonaceous surfaces, modification

Carbonaceous Surfaces Modification, Characterization, and Uses for Electrocatalysis... 

For example, the most noteworthy disadvantage of catalytic wet oxidation is the severe catalyst deactivation (Larachi el al., 1999). Hamoudi el al. (1998, 1999) systematically studied the deactivation of Mn02/Ce02 catalyst during wet catalytic oxidation of phenol and the catalyst-surface modifications. It was observed that deactivation was induced mainly by the formation of carbonaceous deposits on the catalyst surface. Ohta et al. (1980) reported that the size of the catalyst particles affected the stabilization of catalytic activity. For granular particles of supported copper oxide, the catalytic activity was decreased after each inn, even after six successive experiments. In contrast, for larger particles the catalytic activity was stabilized after the first three runs. 

Srinivas B. (2004) Surface modification of carbonaceous materials by introduction of gamma keto carboxyl containing functional groups, US6831194. 

Hemoproteins are a broad class of redox-proteins that act as cofactors, e.g. cytochrome c, or as biocatalysts, e.g. peroxidases. Direct ET between peroxidases such as horseradish peroxidase, lactoperoxidase," or chloropcroxidasc"" and electrode surfaces, mainly carbonaceous materials, were extensively studied. The mechanistic aspects related with the immobilized peroxidases on electrode surfaces and their utilization in developing biosensor devices were reviewed in detail. The direct electrical contact of peroxidases with electrodes was attributed to the location of the heme site at the exterior of the protein that yields close contact with the electrode surface even though the biocatalyst is randomly deposited on the electrode. For example, it was reported " that non-oriented randomly deposited horseradish peroxidase on a graphite electrode resulted in 40-50% of the adsorbed biocatalyst in an electrically contacted configuration. For other hemoproteins such as cytochrome c it was found that the surface modification of the electrodes with promoter units such as pyridine units induced the binding of the hemoproteins in an orientation that facilitated direct electron transfer. By this method, the promoter sites induce a binding-ET process-desorption mechanism at the modified electrode. Alternatively, the site-specific covalent attachment of hemoproteins such as cytochrome c resulted in the orientation of the protein on the electrode surfaces and direct ET communication. ... 

Although numerous reviews on the characteristics of carbonaceous materials have been published [51-54,59-63], in this chapter we focus on a detailed description of carbon surface chemistry and its importance for catalytic processes and those involving reactive adsorption. Thus, the classification of surface groups is followed by an overview of methods of surface modification and characterization, with a brief description and examples of their role in reactive adsorption and catalysis. 

Industrial applications of nanoporous carbons are based on both their porosity and surface properties, and consequently, their characterization is of great importance. The results presented here demonsfrate a great usefulness of gas adsorption measurements for the characterization of nanoporous carbons. Low-pressure measurements provide an opportunity to study the microporous structure and surface proptaties of these materials and to monitor changes in these properties that result fiom structure and surface modification. High-pressure adsorption data allow for a detailed characterization of mesoporous structures of carbonaceous porous materials, providing their surface areas and pore size distributions. 

With few exceptions, the additives that are intended for the modification of the SEI usually have high reduction potentials, which ensure that these additives are reduced on the anode surface before the bulk electrolyte components are involved. In other words, during the first charging of a lithium ion cell, an SEI with the chemical signature from an additive would have been formed before the potential of the carbonaceous anode reached the onset reduction... 

Hydrogenolytic reactions can also be suppressed by carbonaceous layer deposition or by modification of the active surfaces by — for example — sulphur. Suppression of hydrogenolysis gives more chance to a reaction the rate of which decreases only proportionally to the active metal surface concentration, like hydro/dehydrogenation, or some forms of isomerisation (5C cyclic mechanism see the chapter on elementary steps). 

Solid icy surfaces are observed both in the interstellar medium as mantles on silicatic or carbonaceous grains and on many objects in the Solar System." In space, these icy targets are continuously bombarded by energetic ions from solar wind and flares, planetary magnetospheres, stellar winds and galactic cosmic rays. When an energetic ion collides with an icy target produces physico-chemical modifications in the latter. The study of those effects is based on laboratory ion irradiation experiments carried out under physical conditions as close as possible to the astrophysical ones. 

The rate of the oxidation process is determined by the reactivity of the starting carbon and oxidizer. The greater the reactivity of the substrates the lower the temperature of the process in which uniform formation of the pores in the granules is observed. In the case of carbonaceous materials the cokes of brown coals show the greatest reactivity, and the cokes of hard coals the smallest activity. The cokes of pit coals show an intermediate reactivity. This is connected with the earlier mentioned ordering of the crystallographic structure of carbon, which is of significant importance in the case of modification of carbon deposits contained in the carbon-mineral adsorbents in which the carbonaceous compound may be characterized by a differentiated chemical and physical structure. Thus the surface properties of hydrothermally modified complex adsorbents are defined by the course of three processes ... 

There are two problems here, namely, NO inhibits hydrocarbon adsorption, thus the amount of N2O is large and second, surface can be poisoned by carbonaceous species. These two factors can be controlled by the proper selection or modification of the catalyst system. 

Two main topics are selected (1) study of the surface chemistry of raw carbonaceous materials, their behavior during thermal treatment (pyrolysis) and oxidation (2) study of the modifications of surface chemistry after chemical treatments, such as nitrogenation or halogenation. 

XPS was used to study the modifications of the surface chemistry of carbonaceous materials after chemical treatments [111]. For example, recent studies were devoted to the preparation of active carbons modified by incorporation of nitrogen aiming at the development of new solid catalysts [33,34], new catalyst support materials [155], and new competitive adsorbents [111]. 

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