Fuel Cells

A fuel cell is a galvanic cell that uses traditional combustive fuels, most often hydrogen or methane, that are continuously fed into the cell along with an oxidant. (An alternative, but not very popular, name for a fuel cell is a flow battery.) Within the cell, fuel and oxidant undergo the same redox chemistry as when they are combusted, but via a catalyzed electrochemical that is significantly more efficient. For example, a typical hydrogen fuel cell uses graphite electrodes embedded with platinum-based catalysts to accelerate the two half-cell reactions:

In this hydrogen fuel cell, oxygen from the air reacts with hydrogen, producing water and electricity.

Anode: 2H2(g) ⟶ 4H+(aq) + 4e

Cathode: O2(g) + 4H+(aq) + 4e ⟶ 2H2O(g)

Cell: 2H2(g) + O2(g) ⟶ 2H2O(g) Ecell~1.2V

These types of fuel cells generally produce voltages of approximately 1.2 V. Compared to an internal combustion engine, the energy efficiency of a fuel cell using the same redox reaction is typically more than double (~20%–25% for an engine versus ~50%–75% for a fuel cell). Hydrogen fuel cells are commonly used on extended space missions, and prototypes for personal vehicles have been developed, though the technology remains relatively immature.

Watch this video to learn more about fuel cells.