wmmullaney said:
How much hydrogen can you get from a solar powered splitter?
Or just for a test, a 9v battery?
First, you need to decide whether you want the answer as determined by conventional chemistry or by methods used by those who believe in over-unity production, mystical properties of "brown gas," etc.
The following calculation is based on conventional chemistry. For more detail, see these links (among hundreds):
**broken link removed**
**broken link removed**
For those who are not too picky and don't want to get wound up in what are basically unit conversions, consider the following equations:
H2O = H2 + ½O2 Eo = 1.229 V ; and
2H+ +2e- = H2
To get one molecule of hydrogen, H2, from 2H+ you have to provide 2 electrons.
A mole of hydrogen occupies 22.4 L at STP (approximately 29.92 inches of Hg at 32° F
) and contains 6.02X10E23 molecules. Thus, a mole of H2 requires 12.04X10E23 electrons to produce.
Doing the math, production of 1L of hydrogen requires 5.4X10E22 electrons or approximately 8,700 coulombs.
Assume your 9V battery is rated for 500 mAH ( I am too lazy to look up a real value). An hour is 3600 seconds. A current of 0.5 A for 3600 seconds is 1800 coulombs.
Thus, your 1800-coulomb-capacity battery will produce a maximum of 200 mL of hydrogen gas at STP. Efficiency is probably a lot less than 100%, so individual results may vary.
If you are more comfortable with electrical nomenclature, the Faraday is 96,489 coulombs per mole. Since production of H2 reuires 2e per mole of gas, then 192,978 coulombs are required per mole of gas. At STP, a mole is 22.4 L (same as above), so a liter will require 8600 coulombs. The difference is due to rounding.
The simple answer: A 9-V non-rechargeable battery is an expensive way to produce just a little hydrogen.
John
edit: better defined which battery type