The imminent exhaustion of our fossil fuel reserves means that to maintain a constant flow of energy for heating our homes, running our cars etc. we have to find alternative sources of energy. One alternative that has been tried and tested is that of fuel cells. A fuel cell converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol and ethanol are sometimes used. Fuel cells are different from batteries in that they require a constant source of fuel and oxygen to run, but they can produce electricity continually for as long as these are supplied. Batteries will stop once their chemical constituents are exhausted through chemical reactions and are either discarded or have to be recharged. Fuel cells are refuelled rather than recharged.
The half-cell reactions taking place in a fuel using hydrogen as the fuel are as follows:
At the negative electrode:
H2(g) 2H+(aq) + 2e
At the positive electrode:
2e + O2(g) + 2H+(aq) H2O(l)
The overall reaction is therefore:
H2(g) + O2(g) H2O(l)
Therefore the product of the reaction is water which will not pollute and is not a greenhouse emission. The electrical energy produced in the reaction can then be used to power motor cars and other devices.
In the latest edition of the SEP periodical Catalyst, there is a very good article on fuel cells by Michael Whiteley. In this article (written primarily for Key stage 4 but also very good for A-level reviewing of the topic) he gives some historical background and lists and explains the advantages and disadvantages of using fuel cells as a means of generating electrical energy. With regards to the Chemistry Curriculum fuel cells are certainly an important component and are an excellent way of reviewing work on alternative energy and electrochemistry. As with all topics teachers could simply teach the theory of fuel cells without giving students the opportunity to see a fuel cell in action. However, it is always better for students to see these things in action, preferably if they can the practical themselves.
At EDULAB we have always said that our products are directed towards the curriculum and fuel cells is not an exception to this approach. We have a number of products that provide practical experience for students in this area.
The leXsolar range of products provides excellent tools for teaching alternative energy. There are three leXsolar products designed to give students direct experience of the production of hydrogen along with oxygen and their subsequent reaction in a fuel cell:
The leXsolar H2 basic takes a simple, qualitative look at hydrogen fuelled fuel cells. Using this kit, students split up water and then use the hydrogen and oxygen produced to run a fuel cell that produces electricity that can power a motor and produce sound energy from a buzzer. This kit will produce enough knowledge and understanding for KS3 and basic GCSE studies.
A more quantitative approach is possible with the leXsolar H2 intermediate. It can be used to show the production of hydrogen and oxygen using energy from a solar cell and the subsequent use of these gases to produce the required reaction for the fuel cell. This kit is probably more geared for GCSE and A-level Chemistry.
leXsolar H2 advanced goes even further and incorporates into its components a methanol fuel cell. When used to its maximum this kit can be used in an advanced BTEC or degree level course.
As well as the leXsolar kits we have the Hydrogen Fuel-cell Demonstration kit. This give a simple but graphic demonstration of the voltage produced in a simple fuel cell.