Specific surface area of electrodes

BET is an important tool for ES characterization because surface area and pore size are both important parameters in determining material capacitance [59]. It is used to determine specific surface areas of electrode materials such as activated carbon and graphene [60]. Pore size measurements enable the estimation of electrochemical effectiveness of an active material when matched to a specific electrolyte [61-63]. Pore size and surface area are also good indicators of structural changes after chemical or heat treatment [64]. 

This difference is the irreversible capacity loss (<2jr). Dahn and co-workers [71] were the first to correlate <21R with the capacity required for the formation of the SE1. They found that <2ir is proportional to the specific surface area of the carbon electrode and, assuming the fonnation of an Li2C03 film, calculated an SEI thickness of 45 5 A on the carbon particles, consistent with the barrier thickness needed to prevent electron tunneling [1,2]. They concluded [71] that when all the available surface area is coated with a film of the decomposition products, further decomposition ceases. 

The micro structured platelets, hold in a non-conducting housing, were realized by etching of metal foils and laser cutting techniques [69]. Owing to the small Nemst diffusion layer thickness, fast mass transfer between the electrodes is achievable. The electrode surface area normalized by cell volume amounts to 40 000 m m". This value clearly exceeds the specific surface areas of conventional mono- and bipolar cells of 10-100 m m. ... 

Since the specific surface area of modem graphite materials is Sv 104 -r- lO m 1 (Sm 10-2 - 104m2g 1 ), it is almost always possible to make an electrode characterized by A > 1 from a mixture of a carbon material and a solid reagent. 

Therefore the utilization of porous materials with high surface areas serving as electrodes enables capacitors to be made with high capacitance. For example, the use of an activated carbon (10 pF cm ) with the specific surface area of 1000 m g gives a capacitance as high as 100 F g . It should be noted that the capacitance measured in a unit cell corresponds to a quarter of the capacitance per unit weight or volume of the single electrode (F g or F cm ), because the... 

The determination of the true specific surface area of the Pt electrode is possible with the analysis of the hydrogen anodic region of the potentiodynamic curve [7]. It amounts to 80 a.u. for macroporous electrode and 840 a.u. for mesoporous one in comparison to the surface of monocrystalline silicon. 

Platinum black is a layer of finely divided platinum that is formed on the surface of a smooth platinum electrode by electrolytic deposition of the metal from a solution of chloroplatinic acid, H2PtCl6 The platinum black provides a large specific surface area of platinum at which the H /Hi reaction can occur. Platinum black catalyzes the reaction shown in Equation 18-9. Remember that catalysts do not change the position of equilibrium but simply shorten the time it takes to reach equilibrium. 

Figure 18-6 shows how a hydrogen electrode is constructed. The metal conductor is a piece of platinum that has been coated, or platinized, with finely divided platinum (platinum black) to increase its specific surface area. This electrode is immersed in an aqueous acid solution of known, constant hydrogen ion activity. The solution is kept saturated with hydrogen by bubbling the gas at constant pressure over the surface of the electrode. The platinum does not take part in the electrochemical reaction and serves only as the site where electrons are transferred. The half-reaction responsible for the potential that develops at this electrode is... 

In Fig. 29a), the capacitance per gram of carbon electrode in a capacitor is plotted against the specific surface area of the ACFs used [82]. At room temperature, a linear relationship is observed, revealing that a Mgh surface area is desired for Mgh capacitance. At low temperatures, carbon fibers with a relatively low surface area do not give capacitance,... 

The chemical and physical methods of activation allow to produce carbon materials with a highly developed specific surface area. Therefore, activated carbons are extensively used as electrode materials for supercapacitors [11,25,30-37]. Considering Eq. (1) showing that capacitance depends on the surface area of the electrodes, it should be expected that higher the specific surface area of an activated carbon, higher the capacitance. However, practical... 

It follows from all above said that carbon particles interact with the lead active mass, being adsorbed on its surface and/or incorporated in the bulk of the lead skeleton branches. This results in macrostructural changes (reduced median pore radius and increased specific surface area of NAM). Thus, carbon additives alter the very nature of the lead electrode, converting it into a lead—carbon electrode, which will inevitably affect its electrochemical behaviour. The latter will depend on the affinity of carbon to lead, on the electrical conductivity of the carbon additive and on the electrochemical properties of the carbon surface. 

Given that the density of electrodeposited nontemplated vanadia is 2.87 g cm , the average density of double-gyroid structured vanadia with a volume fraction of 37.9 % is1.09 g cm, illustrating the porous nature of the DG structure [16]. Thus, the specific surface area of DG-structured V2O5 is 1.48 m g . Furthermore, the mass m of vanadia electrodes was calculated using these densities, the electrode area and thickness. The V2O5 film thickness was determined by cross-sectional SEM or with a surface profilometer. 

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