Fuel cell reactions, table

Table 2-2 Fuel Cell Reactions and the Corresponding Nernst Equations...

Component enthalpies are readily available on a per mass basis from data such as JANAF (4). Product enthalpy usually includes the heat of formation in published tables. A typical energy balance calculation is the determination of the cell exit temperature knowing the reactant composition, the temperatures, H2 and O2 utilization, the expected power produced, and a percent heat loss. The exit constituents are calculated from the fuel cell reactions as illustrated in Example 10-3, Section 10. 

The spent oxidant composition is calculated in a similar manner. We note that in both the PAFC and PEFC the water is generated on the cathode (air) side. This can be seen from the cathode reaction listed below and the following table listing the fuel cell reaction quantities. 

Thus, 85%, or 5.30 lb mol CH4 /h, will be reformed and consumed by the fuel cell. The remainder will be reformed but not consumed by the fuel cell reaction. We will summarize these changes in the following table. 

Table 16 Thermodynamic Characteristics and Voltages of Fuel Cell Reactions at 650°C...

Table 1 Thermodynamics and theoretically reversible cell potential for fuel cell reactions... 

If the change in the Gibbs free energy AG is greater than the changes in the enthalpy AH, the thermodynamic efficiency can exceed 1 (or 100%). Table 2 also lists the thermodynamic efficiencies for fuel cell reactions of interest under standard conditions. 

In Table 17.3 we have listed the thermodynamic properties (at 25 °C) of several reactions that would be desirable as fuel cell reactions. Each of the oxidizable substances... 

The development of new electrocatalytic materials by deposition of foreign atoms on a host metal is currently a very active area of research in electrochemistry. In this regard, most of the studies have been focused on platinum as a substrate, due to the very high reactivity of this metal for fuel-cell reactions. Still, a surface modifier is necessary to improve the catalytic activity and stability of the electrode and to avoid side poisoning reactions. It has been shown that the modification of platiniun surfaces with submonolayer amounts of elements of the p-block of the periodic table leads, in many cases, to electrode materials with greatly improved catalytic properties. ... 

Direct Akohol Fuel Cells (DAFCs), Table 2 Distribution of the reaction products resulting from the oxidation of 2 M ethanol at 80 °C after 4 h working at a current density of 32 mA.cm for PtSn and PtSnRu catalysts or of 8 mA.cm fin Pt... 

Hydrogen Storage Materials (Solid) for Fuel Cell Vehicles, Table 2 Some reactions with chemical hydrides. The hydrogen density is calculated based on the reuse of the water from the combustion... 

Table 1.7. Change in Gibbs free energy, reversible cell voltage, and efficiency limit (HHV basis) of hydrogen fuel cell reaction at different temperatures [26]. (From Larminie J, Dicks A. Fuel cell systems explained. 32003 John Wiley Sons Limited. Reproduced with permission.)...

Table 3.2. Measured and simulated io of the HOR in a PEM fuel cell [8, 47]. (Data reprinted from Electrochimica Acta, 52.7, Song C, et al., PEM fuel cell reaction kinetics in the temperatme range of23-120 C, 2552-61 and from Journal of Power Sources, 172.1, Zhang J, et al.. Polybenzimidazole-membrane-based PEM fuel cell in the temperature range of 120-200 C, 163-71, both 2007, with permission from Elsevier.)...

Table 1.2 Thermodynamic data for various overall fuel cell reactions at 25 C...

Table 9.5 Values of standard cell voltages of selected fuel cell reactions at 25°C...

Table 3.5 Important Thermodynamic Data on Various Fuel Cell Reactions under Standard Conditions...

This equation seems straightforward and simple enough. However, the Gibbs free energy of formation is not constant it changes with temperature and state (liquid or gas). Table 2.1 below shows Agy for the basic hydrogen fuel cell reaction... 

As discussed in Section 8.4.1, the charge transfer resistance (Rt), expressed by the first right-hand term in Eqn (8.16), can be simulated from the AC impedance spectra based on the equivalent circuit shown in Fig. 3.11 of Chapter 3. Figure 8.7 shows the simulated Rt as a function of current density at 120 °C and 1.0 atm backpressure with different cathode gas inlet RHs. It can be seen that Rt decreases with increasing RH, which indicates that the fuel cell reaction kinetics at higher RHs is faster than at lower RHs. This is consistent with the trend in the dependence of Iq and on RH, as observed in Table 8.1. 

There are different types of fuel cells classified by the different electrolyte materials used as described in Chapter 1. The anode and cathode reaction characteristics are therefore different in each fuel cell type. Table 4.1 shows a... 

The comparison of various techniques used for the analyses of methanol and ethanol electro-oxidation at anode and the results are given in Tables 2 to 3 for methanol and ethanol, respectively. The most commonly used technique in electrochemical studies of fuel cell reactions has been cyclic voltammetry. The cyclic voltammetry is used to study the redox behavior of electrodes in fuel-electrolyte solutions (Bard et al. 2001). The cyclic voltammogram helps to identify the reaction intermediates, poisoning species, reaction mechanism, suitable combination of electrode material and electrolyte/fuel mixtures, such that the formation of poisoning species is prevented. Prabhuram et al. (1998) investigated methanol oxidation on unsupported platinum electrodes in alkaline condition (Table 2). The cyclic voltammograms (CVs) were recorded in... 

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