Standard hydrogen/oxygen fuel cell

A hydrogen/oxygen fuel cell, operating at near-standard conditions to produce liquid water as the reaction product, delivers 50 A at 0.70 V. What is the efficiency of the cell ... 

Using the standard free energies of formation in Appendix B, calculate the standard cell potential for the reaction in the hydrogen-oxygen fuel cell ... 

With gaseous water the cell voltage at equilibrium of a hydrogen-oxygen fuel cell at 25°C under standard conditions is E°eq = 1.18 V, since AG°as = -227 kJ mol-1 at 25°C. 

Professor S. Srinivasan and his team have studied the effect of pressure and characteristics of the current-potential relations in a hydrogen-oxygen fuel cell with a proton exchange membrane (Y. W. Rho, O. A. Velev, S. Srinivasan, and Y. T. Kho,./. Electrochem. Soc. 141 2084, 2089, 1994). In this problem, it is proposed to study the applicability of the theoretical dependence of the cell potential as a function of pressure. The temperature is 25 °C and it may be assumed that the pressure of the gas in each of the compartments, i.e., the anodic compartment (hydrogen) and the cathodic compartment (oxygen), are the same, Pn =Po P- For the formation of water in its standard state, the relevant thermodynamic quantities are ... 

Figure 3.3.8 Schematic illustration of the origin of activation overpotentials in a hydrogen-oxygen fuel cell. The solid curves represent exponential analytic current densities versus electrode potential of the hydrogen electrode (standard potential 0 V) and the oxygen electrode (standard potential 1.23 V). Relevant for a PEMFC fuel cell are the HOR (anode) and the ORR (cathode) branches. To satisfy a cell current (yceii), the anode potential moves more positive by riact,HOR> while the cathode potential moves more negative by iiact.oRR- As a result of this, the observed cell potential is V, which is smaller than 1.23 V. The shape of the individual characteristics is such that the cathode overpotentials are larger than those at the anode.

These equatioirs irray be applied to a hydrogen/oxygen fuel cell operating at 298.15 K (25 °C) aird 1 bar with pure Hi aird pure O2 as reactairts aird pure H2O vapor as product. If these species are assumed ideal gases, then tire reactioir occurring is the standard formation reaction for H20(g) at 298.15 K (25°C), for wlriclr values from Table C.4 are ... 

What is the maximum work that can be obtained from a hydrogen-oxygen fuel cell at standard conditions that produces 1.00 kg water at 25°C Why do we say that this is the maximum work that can be obtained What are the advantages and disadvantages in using fuel cells rather than the corresponding combustion reactions to produce electricity ... 

The hydrogen-oxygen fuel cell has a standard emf of 1.23 V. What advantages and disadvantages there to using this device as a source of power compared to a 1.55-V alkaline battery ... 

H aq), E° = -0.064 V. This reaction is not spontaneous under standard conditions, but it is spontaneous when the concentrations of products are sufficiently low. lead-acid battery 83.42 A h/kg hydrogen-oxygen fuel cell 2 975 A h/kg... 

Equilibrium potential of the oxygen electrode (V), Equation 1.5 Equilibrium potential of the hydrogen/oxygen fuel cell at standard conditions (V), Equation 1.8... 

The maximum cell voltage (E°), or the theoretical potential of fuel cell, for the hydrogen/air fuel cell reaction at a specific temperature and pressure is calculated by E = - AG / nf, where n is the number of electrons involved in the above reaction, and F is the Faraday s constant. Since AG° (237,340 Jmor ) n and F are all known, the theoretical hydrogen/oxygen fuel cell voltage can be calculated. Under standard condition (1 atmosphere press and 298 K), the maximum fuel cell voltage is given as... 

For a hydrogen/oxygen fuel cell p = 101.3 kPa, where at standard conditions, T = 298 K and... 

What is the theoretical standard cell voltage, E n, of each of the following voltaic cells (a) the hydrogen-oxygen fuel cell described by equation (19.26) (b) the zinc-air battery (c) a magnesium-iodine battery. 

Suppose a hydrogen-oxygen fuel-ceU generator produces electricity for a house. Use the balanced redox reactions and the standard cell potential to predict the volume of hydrogen gas (at STP) required each month to generate the electricity. Assume the home uses 1.2 X itf kWh of electricity per month. 

Figure 14.10 gives a schematic presentation of the current-voltage characteristics of hydrogen and oxygen on platinum. The theoretical open circuit cell voltage at 25 °C and standard conditions is 1.229 V, for both the fuel cell and electrolyzer. 

Schematic depiction of seven-layer structure and basic processes in polymer electrolyte fuel cells under standard operation with hydrogen and oxygen.

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