Nowadays, more and more attention is paid to the possibilities for the conversion of fuel energy directly to electric energy, which could reduce energy losses. Using fuel cells is one such possibility.
Fuel cells are voltage sources in which electrical energy is directly produced from the energy released by the oxidation of a fuel (hydrogen, methane, methanol, etc.). Unlike a battery fuel cells can be continuously fed with fuel.
In the fuel cell model demonstrated in this experiment, hydrogen is used as the fuel and oxygen as the oxidant. A V-shaped glass reactor was filled with diluted sulfuric acid solution. Two large-area platinum sheets were inserted into the solution. Platinum was used for the electrodes because it adsorbs (or absorbs) hydrogen as well as oxygen and is, therefore, an effective catalyst.
One electrode compartment was fed with oxygen, and the other with hydrogen. Glass frit behaved as a membrane, preventing the mixing of oxygen and hydrogen, but ions in solution still go through.
The following equations describe the working principle of this fuel cell:
1) On (-) electrode which is the anode:
a) Molecular hydrogen (H2) adsorbs (or absorbs in platinum) on platinum surface as atomic hydrogen (Hads):
H2(g) → 2Hads(Pt)
b) Atomic hydrogen oxidizes, releasing electrons:
2Hads(Pt) ↔ 2H+(aq) + 2e-
2) On (+) electrode which is the cathode:
a) Oxygen (O2) adsorbs (or absorbs in platinum) on platinum as atomic oxygen (Oads):
O2(g) → 2Oads(Pt)
b) Atomic oxygen reacts with protons and electrons from the external wire, yielding water as a product:
4H+(aq) + 4e- + 2Oads(Pt) → 2H2O(l)
Therefore, by closing the circuit:
1) Electrons move from anode to cathode.
2) Protons move from the anode compartment through the membrane into the cathode compartment.
In total, taking into account all anode and cathode processes, we get a simple hydrogen combustion reaction:
2H2(g) + O2(g) → 2H2O(l)
However, in case of a fuel cell, the reaction mechanism is more complex. Nowadays, extensive research is ongoing on fuel cells as they offer an alternative to burning fossil fuels. Still, fuel cells are not yet very widespread because of their high price and some technical problems. Several companies have started producing fuel cells, which power electric cars, buses or even ships.