Question

a hydrogen-oxygen fuel cell is used in the space program to generate clean energy. Describe, in detail, the principle and process of electrical energy generation from hydrogen-oxygen fuel cell. Also include in the discussion major advantages and limitations of such fuel cells.

Answer 1

hydrogen-oxygen fuel cell :- The cell consists of two porous carbon electrodes impregnated with a suitable catalyst such as Pt, Ag, CoO, etc. The space between the two electrodes is filled with a concentrated solution of KOH or NaOH which serves as an electrolyte. H₂ gas and O₂ gas are bubbled into the electrolyte through the porous carbon electrodes.

Thus the overall reaction involves the combination of hydrogen gas and oxygen gas to form water.

The cell runs continuously until the reactant's supply is exhausted.

This type of cell operates efficiently in the temperature range 343 K to 413 K and provides a potential of about 0.9 V.

It was used as a primary source of electrical energy in the Apollo space program.

advantage :-

Hydrogen fuel cells offer an alternative to rechargeable cells and batteries.

Fuel cells do not produce the usual pollutants like sulfur oxides (acid rain), nitrogen oxides and carbon monoxide (harmful gases from traffic pollution).

Fuel cells can be made reasonably lightweight and compact saving both space and weight.

Hydrogen-oxygen fuel cells create water and since the hydrogen will have to be made from abundant water supplies in the long run, it is effectively a renewable resource, unlike fossil fuels like petrol or diesel.

Fuel cells are much more efficient than fossil fuel power stations or costly chemical batteries etc. because the electrical energy is generated directly from the chemical reaction.

In fossil fuel power stations, motor vehicles, coal/gas fires etc. too much energy is lost as waste heat.

With a fuel cell there are fewer stages in producing the useful electrical energy, so there is less chance of losing useful energy e.g. waste heat, friction from moving parts.

disadvantages

Fuel cells cannot be used for large–scale energy production, so conventional fossil fuel or nuclear power stations still have an important future.

Hydrogen is a gas and requires a much larger storage volume compared to fossil fuels like petrol.

Safe storage is an issue, especially as it would be stored under high pressure to decrease the storage space required.

This immediately makes leaks and accidents more likely to happen because hydrogen is a highly flammable explosive gas – too easily ignited, remember the 'squeaky pop' lit splint test for hydrogen!

There is no efficient means of mass producing hydrogen