Carbon black electrochemical oxidation

The studies by Biermann et al. [28] indicate that the carbon blacks used as the conductive matrix in Leclanche cells remain chemically inert, that is, they do not undergo oxidation during storage or discharge of the cell. However, Caudle et al. [29] found evidence that the ion-exchange properties of carbon black, which exist because of the presence of surface redox groups, are responsible for electrochemical interactions with Mn02. The extent of MnO, reduction to MnOOH depends on the carbon black (i.e., furnace black > acetylene black). 

One of the common ways in which fuel cell components experience degradation is through corrosion. Carbon particles in the CL are susceptible to electrochemical (voltage) corrosion and contain Pt particles that catalyze oxidation reactions. The carbon fibers in CFPs and CCs and the carbon black in MPLs are not as susceptible to these issues because they are not part of the electrochemical reactions and do not contain Pt particles. However, they can still go through chemical surface (hydrogen peroxide) oxidation by water or even by loss of carbon due to oxidation to carbon monoxide or carbon dioxide [256,257]. 

Carbon is used in lithium-ion cells for different functions conductive carbon black and/or graphite additives are applied in both the negative and the positive electrode to improve the electronic conductivity of the electrodes. These conductive additives constitute a fraction of up to about 10% of the total carbon consumption. The major fraction is represented by the active carbon materials which are electrochemically reduced and oxidized in the negative electrode during the battery charge and discharge process, respectively. 

Boudenne, J. L., Cerclier, O., Galea, J. and Vlist, E. V. D. (1996) Electrochemical oxidation of aqueous phenol at a carbon black slurry electrode. Appl. Catal. A General 143, 185-202. 

Heckman and Harling57 examined the gas-phase oxidation of carbon black micro-structures and showed that oxidative attack of carbon crystallites was concentrated on the small crystallites, at the edges of layer planes and at lattice defects. Partial graphitization of a carbon black, so that only the outermost surface layers are well-ordered, causes oxidative corrosion within the core of the carbon particle, leaving an outer shell . Consequently, similar behavior can be expected for ungraphitized and partially graphitized carbons in electrochemical environments. 

Cyclic voltammetric methods have been used for investigating surface oxygen compounds present on the surface of unmodified carbon materials, and in some cases, previously oxidized materials (electrochemically, oxygen rf-plasma, air, and steam), such as carbon blacks 9,10), gla.sslike carbon [11-15], graphite [16,17], carbon fibers [18-21], pyrolytic carbon [22,23] and active carbon [24-28],... 

Nanoparticles have also been used successfully as amperometric gas sensors. Chiou and co-workers developed a dispersed catalyst gas-diffusion electrode for SO2 sensing [195]. Chloroauric acid is adsorbed on carbon black and subsequently reduced in a stream of hydrogen to obtain nanometer-sized particles. These are then shaped in the form of an electrode and used as a sensor. The electrochemical oxidation of SO2 gas is catalyzed by the nanoparticles with a fast response time. A... 

Important processing methods Langmuir-Blodgen teclinique of monolayer production, solution polymerization over the substrate, electrochemical anodic polymerization, chemical oxidation of pyrrole in carbon black suspension... 

Kinoshita, K. and Bett, J. (1973). Electrochemical oxidation of carbon black in concentrated phosphoric acid at 135C. Carbon, 11, 237. 

The Miilheim electrochemical method of producing R4N+X -stabUized transition metal colloids is a viable alternative to the traditional chemical process. The preparation of aqueous colloidal solutions of nanosized transition metal oxides or multimetal oxides (1-3 nm) is possible by an unusually simple procedure, namely hydrolysis of the corresponding metal salts under basic conditions in the presence of water-soluble stabiUzers. High concentrations (0.1-0.5 M) are usually possible, which is crucial for industrial applications. In many cases an in situ method for immobUization on a soUd carrier such as carbon black is possible in the absence of a stabUizer. In the rare case of IrO, the colloidal soluhon (2nm) is stable for... 

The electrochemical oxidation of carbon black in 96% phosphoric acid has been studied at 135 °C. Two anodic processes were observed to occur (a) the formation of a surface oxide, and (6) the evolution of CO2. Both processes decreased with time but at different rates, so that CO2 evolution eventually became the major reaction. 

Although in situ infrared spectroscopy has been applied widely in terms of the systems studied, the reflective electrodes employed have been predominantly polished metal or graphite, and so an important advance has been the study of electrochemical processes at more representative electrodes such as Pt/Ru on carbon [107,122,157], a carbon black/polyethylene composite employed in cathodic protection systems [158] and sol-gel Ti02 electrodes [159]. Recently, Fan and coworkers [160] took this concept one step further, and reported preliminary in situ FTIR data on the electro-oxidation of humidified methanol vapor at a Pt/Ru particulate electrode deposited directly onto the Nafion membrane of a solid polymer electrolyte fuel cell that was mounted within the sample holder of a diffuse reflectance attachment. As well as features attributable to methanol, a number of bands between 2200 and 1700 cm were observed in the spectra, taken under shortoperating conditions, the importance of which has already been clearly demonstrated [107]. 

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