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Analysis:
Before going on to explain the electrolysis process, note that the solar panel is delivering nearly
half a watt (0.470) into the fuel cell load. This is less than the nearly three-quarters of a watt
delivered with the battery in Experiment #1. The reason for this decrease is due to the solar
panel’s inability to produce the same amount of power as compared with the battery. If sun was
not used in this experiment to energize the solar panel, the actual power would be even less. If a
larger solar panel were used, the power would certainly be increased.
In terms of the electrolysis process, the minimum voltage at which water can be split into
hydrogen and oxygen is called the “decomposition voltage”.
Scientists have determined that the theoretical decomposition voltage for water is 1.23 volts,
which is lower than what this experiment shows. The difference between the theoretical
decomposition voltage and the measured voltage is called “overpotential”. Overpotential is a
function of the fuel cell’s inability to expel the hydrogen and oxygen gasses that form on the metal
electrodes below a certain voltage; in this case, about 1.5 volts as compared with 1.23 volts.
Many other factors are involved in this difference of decomposition voltage; however, the reasons
for these differences are beyond the scope of this experiment.
What this experiment demonstrates is the relatively small amount of voltage necessary to split
water into its component gasses of hydrogen and oxygen. This fact should be remembered when
dealing with fuel cells in future experiments.
