Hydrogen-Oxygen Fuel Cells: Case Study

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HSC Chemistry Research Assignment

Topic: The Production of Materials

Lloyd Ruz

Cell Type: Hydrogen-Oxygen Fuel Cell

The structure of the cell

The Hydrogen-Oxygen Fuel cell uses hydrogen as its fuel source. The basic structure of such a fuel cell is outlined below:

Figure 8A

The chemistry of this cell will be outlined below.

The chemistry and function of the cell

Two separate half-cell reactions occur to produce a flow of electrons (current):

  • At the Anode, Hydrogen gas is oxidised, allowing protons (H+) to enter the proton exchange membrane (or polymer electrolyte membrane, coincidentally, both mean the same thing, in this case, and have the same abbreviation: PEM) and electrons (e-) to travel around a circuit to the cathode. Hence the following oxidation reaction takes place:

  • At the Cathode, protons that have permeated through the membrane and oxygen molecule which has dissolved through the electrode are reduced by electrons that have completed the circuit. Hence, the following reduction reaction takes place:

 .    .    .    .    .    .    .    .   (1,5,6,7,8)

These reactions and the flow of electrons are shown in Figure 8A (above) and again below in Figure 9

Figure 9

When the electrolyte is an alkaline (as in a Alkaline fuel cell with an anion exchange membrane), such as in Figure 6A (below), the following half reactions take place:

Anode:         H2(g) + 2OH(aq) → 2H2O(l) + 2e

Cathode:         O2(g) + 2H2O(l) + 4e→ 4OH(aq)    .    .    .    .    .   .   (5,11)

Figure 6B

A Hydrogen-Oxygen Fuel Cell with alkaline electrolyte. Such as is commonly found in space-craft.

In both cases the net reaction (for a hydrogen-oxygen fuel cell) is the same as the combustion of Hydrogen. (5,11) (however, since hydrogen never comes in direct contact with oxygen, it is not actually combusted):

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2H2(g) + O2(g) → 2H2O(l)                        (5,11)


Applications of the cell

The hydrogen-oxygen fuel cell is (in terms of energy sources) a relatively new technology. This means that while it is available in some commercial situations, research is still being conducted to improve efficiency and expand potential applications. Several applications that either exist or are being researched include:

  • Use in Space-Craft
  • Use in new ‘clean’ automobiles
  • Powering Houses
  • Powering Medium sized portable devices (eg. Laptops)

The use and suitability comes down to the type of fuel cell, efficiency and cost. Space craft fuel cells are usually alkaline cells whereas ...

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