Practical – Hydrogen Fuel Cell
Fuel cells are relevant to the AQA, OCR and Edexcel chemistry curricula, but also bridge environmental issues in other subjects such as physics, biology and geography.
| AQA | unit 5, understand the electrode reactions of a hydrogen-oxygen fuel cell and appreciate that a fuel cell does not need to be electrically recharged, appreciate the benefits and risks to society associated with the use of these cells |
| Edexcel (GCSE) | 5.21 – 5.22 Recall that a simple fuel cell combines hydrogen and oxygen to form water and that this reaction releases energy. Evaluate the advantages and disadvantages of using hydrogen, rather than petrol, as a fuel in cars |
| OCR Salters | F331, Applications – understand the work of chemists in improving fuels and in searching for and developing fuels for the future including use of oxygenates and the hydrogen economy; |
Making your own hydrogen fuel cell helps you to understand the workings of a simple fuel cell – which can be complicated to understand. It is important you get some background context for this, and there are numerous media articles concerning fuel cells. You may be interested in the ultra-modern hydrogen-powered cars that have been developed:
http://www.hydrogencarsnow.com/hydrogencars2010-2011.htm
Key Points
Many fuel demonstrations are based on Combustion to release energy. Fuel can also be oxidised by electrolysis.
They produce electricity from the reaction between a fuel such as an alcohol or hydrogen at the anode, and oxidising agent such as oxygen at the cathode. The fuel and oxidising agent react in the presence of an electrolyte.
Reactants flow into the cell, and products flow out while the electrolyte remains inside the cell. The cell works by catalysis – separating the component electrons and protons of the reactant and fuel and forcing the electrons to travel through a circuit – hence the electrical power. A simple diagram of a fuel cell is key here, which you can sketch and label the key parts.
The fuel cell is fundamentally different to a battery because the reactants can be constantly replenished – it’s a thermodynamically OPEN system compared to a battery which is thermodynamically closed. Typical fuel cell produces ~0.6 – 0.7V but can be combined in series – higher voltage, or parallel – increased current. A parallel connected fuel cell is called a fuel cell stack. Increasing the surface area of the cell can increase the current.
You can also compare and contrast the workings of an alcohol vs. hydrogen fuel cell and discuss the advantages/disadvantages of each i.e. Hydrogen produces only water as a product which is clean, but H2 storage is a problem. Other advantages include excellent reliability in remote areas such as weather stations.
There are many fuel cell demonstrations available for purchase. A reputable seller is h-tec:
http://www.h-tec.com/en/index (more information later)
Extensions:
· Investigating different types of alcohol provided they are water-soluble: including the alcohol series from methanol to pentan-1-ol and their secondary/tertiary isomers.
· Investigation into the effect of changing the initial concentration of alkali on the output voltage. You can also investigate whether changing the type of alkali used makes a difference e.g. NaOH vs. KOH.
HOW TO – Build your own band aid fuel cell
Build a Fuel Cell with a couple of Band Aids, an MEA and a few scraps of stainless steel bug screen by Gavin D. J. Harper.
http://makezine.com/2008/02/29/how-to-build-your-own-ban/
http://www.youtube.com/watch?gl=BR&hl=pt&v=_g7MQe2ufmw
http://www.jmfuelcells.com/products/meas
http://www.jmfuelcells.com/how_to_buy
H-TEC EDUCATION is an internationally renowned provider of teaching and demonstration models as well as course materials in the field of hydrogen and fuel cell technologies. All of these products emphasise science as a lived experience, display outstanding quality, and are highly target group-oriented.
http://www.h-tec.com/en/education/?L=1
http://www.h-tec.com/en/education/home/
Alfa Aesar are the other main company to go to (owned by Johnson Matthey)
