| I took some movies of the whole
experiment. If you click on the links below the file is downloaded and played with the
Windows Media Player. It may take a little while because each movie is 1 minute long (1.3
MB). To hear my comments you need a sound card and loudspeakers or a headphone. |
| If you do not know whether the
movies would play on your computer I propose the following. Click on the link
"Test" which loads a little movie of 5 seconds (120 kB). If your computer plays
it the larger files will work as well. |
| Movie 1 shows the initial state
of the experiment. The 2 platinum wires act as electrodes in the salt solution. A
voltmeter cannot detect any potential difference. Then a battery is connected, and
electrolysis is performed. The voltmeter indicates the battery voltage. |
| Movie 2 starts with the
continuation of electrolysis. Then the battery is taken away. The electrodes now are
"polarised", i. e. a chlorine and a hydrogen electrode because of the adhering
gas bubbles. The reverse reaction of the electrolysis, in this case the formation of HCl,
creates electric energy (represented by the voltage). The cell acts now as "gas
battery" or, in modern terms, as fuel cell. The voltage remains a while on a high
level of approx. 2 volts (due to other effects that are explained in the manual) and then
drops to the expected value of approx. 1.4 volts. All this is only possible due to the
catalytic activity of the Pt electrode surface. |
| Even after some minutes, the
voltage still remains on a level of approx. 1.4 volts. The cell is able to give electric
energy as long as there are gas bubbles (even very small ones) adhered to the platinum
surface. Within the next hour the voltage would slowly drop to low values (but this would
be a very boring movie). Although our device has a very small power output that allows
only to drive a voltmeter - isn't it easy to build a fuel cell and demonstrate and
understand the principles behind? |
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