Fuel cell open circuit voltage

Figure 1.19. Experimental OCV and theoretical OCV corrected for mixed potential and H2 crossover [22], (Adapted from Journal of Power Sources, 163, Zhang J, Tang Y, Song C, Zhang J, Wang H. PEM fuel cell open circuit voltage (OCV) in the temperature range of 23°C to 120°C, 532-7, 2006, with permission from Elsevier.)...

Chapter 7 Fuel Cell Open Circuit Voltage... 

The three-layer sandwich in Figure 1.1 transforms to the two charged capacitors connected in series, which results in a voltage drop between the Pt plates. This system is a hydrogen fuel cell under open-circuit conditions-, the voltage drop between the anode and the cathode Pt plates is called the cell open-circuit voltage (OCV). 

Therefore, AG available in fuel cells can be found in standard thermodynamic tables of fuels. In fuel cells, AG is related to the cell open-circuit voltage Voc by the equation... 

Most of the fuel cell reactions run on the surface of precious catalysts. However, so far none of the catalyst properties has appeared in the equations. The relations above describe the maximum possible cell open-circuit voltage, which is determined solely by the thermodynamics of species involved in the reaction. ... 

In fact, the theoretical cell voltage, is the fuel cell open circuit... 

The standard Nemst potential (E°) is the ideal cell voltage at standard conditions. It does not include losses that are found in an operating fuel cell. Thus, it can be thought of as the open circuit voltage. 

The portion AQ = AH - AG = TAS of AH is transformed into heat. Ideal theoretical efficiencies % determined by the types and amounts of reactants and by the operating temperature. Fuel cells have an efficiency advantage over combustion engines because the latter are subdued to the Carnot limitation. High thermodynamic efficiencies are possible for typical fuel cell reactions (e.g., e,h = 0.83 (at 25°C) for H2 + I/2O2 -> H20(i)). The electrical potential difference between anode and cathode, = -AG/W(f, which is also called the electromotive force or open-circuit voltage, drives electrons through the external... 

Research Focus Synthesis of sulfamic acid electrolytic polymers for fuel cells requiring high proton conductivity and open circuit voltages. 

Another interesting attempt worth noting is the combination of porphyrin sensitized solar cell with a fuel cell made by Moore and Gust. The hybrid cell can realize an open circuit voltage of 1.2 V. The energy conversion efficiency of this photoelectrochemical biofuel cell can, in principle, produce more power than either a photoelectrochemical cell or a biofuel cell working individually [83],... 

The open circuit voltage (OCV) of a fuel cell is identical to the reversible cell potential, provided that the cell is in thermodynamic equilibrium. That is usually achieved, especially at high temperatures. There are some causes which... 

An AFC combined with a lead acid battery has been used in a hybrid vehicle. Between operating times the cell was shut down by using the battery to drain the KOH electrolyte. This technique can improve the life expectancy enormously by protecting the fuel cell from a high open circuit voltage, which otherwise could induce carbon oxidation processes to produce carbonates that would destroy the matrix electrolyte. 

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