Electrochemistry - Hydrogen fuel cells

A hydrogen fuel cell is an electrochemical cell that converts the chemical energy of a fuel, hydrogen ($H_2$), and an oxidizing agent, oxygen ($O_2$), into electricity through a pair of redox reactions.

Unlike a battery, which stores a finite amount of energy, a fuel cell produces electricity continuously as long as fuel ($H_2$) and oxidant ($O_2$) are supplied.

At the anode (negative electrode), oxidation occurs. Hydrogen gas molecules lose electrons to form hydrogen ions ($H^+$).

At the cathode (positive electrode), reduction occurs. Oxygen gas reacts with the hydrogen ions and the electrons arriving from the external circuit to form water ($H_2O$).

The movement of electrons from the anode to the cathode through an external circuit creates the electric current used to power devices.

The only product of the reaction is water ($H_2O$), meaning there are no pollutant emissions like carbon dioxide ($CO_2$) or nitrogen oxides ($NO_x$) at the point of use.

Major disadvantages include the high cost of catalysts like platinum, the difficulty of storing highly flammable hydrogen gas ($H_2$) at high pressure, and the fact that most hydrogen is currently produced from fossil fuels like methane ($CH_4$).