Fuel cells a type of electrochemical cell. They work on the idea that one day they could replace the inefficient conversion of fuels to heat (approx 40%) and then electricity with a more efficient (approx 80 – 85%) and cleaner way of producing electricity. Water is produced as a ‘waste’ product.
They are different electrochemical cells to the ones you will have studied at IB as they are open systems – fuel (in the form of Hydrogen and Oxygen) must be continually added to them to produce electrical power.
There are many different varieties but they all work in very much the same manner. Two inert, porous electrodes (porous to allow gases to diffuse through) are put into a solution of potassium hydroxide with hydrogen (anode) and oxygen (cathode) bubbled into the cell from opposite sides.
The reactions that occur are:
O2 (g) + 2H2O(l) + 4e– → 4 OH–(aq) Reduction (Cathode) E o = +0.40v
2H2 (g) + 4 OH – (aq) → 4H2O (l) + 4 e– Oxidation (Anode) E o = -0.83v
Overall 2H 2(g) + O2 (g) → 2 H2O (l) EMF = Eo RHS – E o LHS = + 0.40 – – 0.83 = +1.23v
Fuel cells are still considered to be in the early stages of their development. There are many design issues. A high inital set up cost as well as temperature management are issues. The highly exothermic reactions that occur act against the cell (according to Le Châteliers principle) and reduces the emf.
Despite these problems organisations such as the California Fuel Cell Partnership have been set up to promote hydrogen vehicles in the state of California.