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微型燃料电池实验手册

2018-4-22 10:54| 发布者: dymodel| 查看: 320| 评论: 0|原作者: baby

摘要: Themini fuel cell can simply be used to demonstrate that it works, and to show a fuel cell's simplicity and such like things. However, the Mini Fuel Cell has also been designed for other more challeng ...
Themini fuel cell can simply be used to demonstrate that it works, and to show a fuel cell's simplicity and such like things. However, the Mini Fuel Cell has also been designed for other more challenging experiments. Five suggestions are given in the "Manual of Experiments". This manual of experiments is presented in electronic form below.
Teachers and lecturers are permitted and encouraged to copy the instructions presented here and to use them in their own worksheets and or laboratory instructions. You will almost certainly need to modify them somewhat for your own use, this is much easier when they are supplied in this electronic form. For this reason this Manual of Experiments is available exclusively in this electronic form.
With your mini fuel cell you should have received a short manual, which gives instructions for the basic care and operation of the cell, and also explains its chemistry. The experiment instructions below sometimes refer to these instructions.
A series of short experiments or demonstrations that compare fuel cell operation with the ordinary burning of fuel. The aim is a thorough understanding of what is going on in a fuel cell. Most rely on the fact that the cathode is at the end of a tube, into which can be put (for example) oxygen, carbon dioxide, or water. 


A series of experiments comparing fuel cell operation with ordinary burning.
Introduction
The purpose of these demonstrations or experiments is to compare what is going on in the fuel cell with ordinary burning. The point to get over is that the fuel is chemically reacting with oxygen in the air, but that electricity is being produced instead of heat and light. 
These experiments can be done by the pupils, if a suitable oxygen supply is available. Alternatively they can be done as a teacher demonstration.
The experiment/demonstrations are very short, and even with the pupils doing their own experiments, and then writing them up, all should be finished within 35 minutes.
The current produced during this experiment will be strongly dependent on the resistance of the meter used. However, in all cases the proportional change in current will be much the same whatever meter is used. An important feature of this fuel cell is that no harm will be done if the cell is "short circuited" by an ammeter, even if the "short circuit" is maintained for weeks on end. 
Apart from the electrolyte, and fuel, the other apparatus and materials needed are:-
liquid fuel anode 
air cathode 
ammeter (0-1 A) 
2 connecting wires 
water 
a supply of oxygen 
a supply of carbon dioxide (optional) 
Instructions 
Take care, this experiment involves the use of methanol (which is poisonous), and KOH solution (which is corrosive).
1) Fill the liquid fuel anode up to the fill line KOH electrolyte (~1 M) BUT DO NOT PUT ANY FUEL IN.
2) Connect the ammeter (0-1A) to the cell, and record the current. (It should be zero.)
3) Add about 10 cm3 of methanol to the cell. Observe the current. (It should rise to about 0.3A). Conclusion. The current is caused by some reaction involving the methanol.
4) Cut off the air supply to the upper electrode (the cathode) by pouring a little water into the air cathode, as shown in the diagram below. Record the effect on the current. (It should fall, after a few seconds, to just above zero.) Conclusion. The reaction causing the current also involves air, just like burning.
 

Note. The current does not fall completely to zero because of the dissolved oxygen in the electrolyte and the water. Note also that the current does not fall instantly because of the electric charge stored in the pores of the electrodes.
5) Pour the water out of the cathode holder, taking care to do this over the sink, so that any drips of electolyte from the cathode do no damage.
6) Get the cell working again. Direct some oxygen into the space above the cathode. Being denser than air, the oxygen will stay in the tube above the electrode. Observe the effect on the current. It should increase noticeably. Conclusion. The reaction causing the current is between the methanol and the oxygen in the air.
7) Discuss with the students the comparisons between this reaction and the burning of methanol. There are similarities, but electricity is produced instead of heat and flame. If necessary repeat one or two of the dramatic "burning things in oxygen " type demonstrations.
8) The comparison with burning could be reinforced by "extinguishing" the fuel cell with CO2. Direct CO2 gently into the space above the cathode. The current will be observed to fall to zero, though it will rise again when the CO2 disperses.


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