What’s a fuel cell?
Fuel cells are electrochemical devices that directly convert chemical energy of a continuous reaction into electrical energy. The chemical energy doesn’t need to be converted into thermal energy and then mechanical energy making it a conversion with hardly any losses so the fuel cell is a very efficient manner of generating energy.
In the cell a redox reaction takes place. In this respect the fuel cell seems to act as a battery, but htere’s an important difference. In a fuel cell repeatedly reagents are supplied from the outside, while the reactants in a battery are stored in a closed system
A fuel cell compromises a porous anode and cathode with an electrolyte layer therebetween. Hydrogen and oxygen are introduced separately from each other to the fuel cell. The hydrogen at the anode and the oxygen (oxidant) to the cathode. In the cell, these two substances are separated by a membrane. With the aid of a catalyst, the hydrogen (H2) at the anode is divided into two H + ions (protons) and two electrons (e-). The electrons then flow through an electric circuit to the cathode, this is the electric current which can be used, for example, empowering an electric motor. The protons flow through the electrolyte to the cathode. The protons and electrons come together at the cathode and react there with the oxygen (O2) which is entered. This produces water (H2O). Below is an overview of the chemical reactions that take place in a fuel cell:
Anode: H2 → 2H + + 2e- Cathode: O2 + 4H + + 4e-→ 2H2O
Whole cell: 2H2 + O2 → 2H2O + energy (electricity and heat)
A single fuel cell supplies, in theory, a voltage of about 1.20 volts, but in practice is that voltage much lower, between 0.5 and 0.8 volts. In order to increase the current, the individual cells are stacked on top of each other and are connected. The stack thus created is called a “fuel cell stack” or “stack”.