A joule equals one watt-second—i.e., the energy released in one second by a current of one ampere through a resistance of one ohm. That sounds like one Volt. 1 amp through 1 ohm can't be done in water. There has to be about 1.5 Volts to ionize the water. I found this very basic experiment that may entertain some folks and may give a clue to the answer to the question.

Electrolysis: Obtaining hydrogen from water: The Basis for a Solar-Hydrogen Economy.

This project involves an experiment in electrochemistry that illustrates several important energy related processes.

Introduction to Electrolysis: Hydrogen from Water

The process by which we generate hydrogen (and oxygen) from water is called electrolysis. The word "lysis" means to dissolve or break apart, so the word "electrolysis" literally means to break something apart (in this case water) using electricity.

Electrolysis is very simple - all you have to do is arrange for electricity to pass through some water between to electrodes placed in the water. Its as simple as that! The principle of electrolysis was first formulated by Michael Faraday in 1820.

Materials you will need

1. A DC power source with a Voltage greater than 1.5 volts or it wont work in tap water.

2. Two pencils. I like to expose a length of the big flat carpenter's pencils. (I used to salvage those big carbon rods from the big No. 6 Dry Cells and clean the nasty stuff off of them. The big carbon rod in the center had screw terminals on them.)

3. Two pieces of electrical wire to connect the power source to the graphite by wrapping or clampin gently on the graphite.

4. A jar full of tap water.

5. An insulated holder for the pencils. A small piece of cardboard to poke them through will do.

6. Tape, electrical or masking if needed.

Tools you will need

1. A sharp blade for gently shaving the wood from the pencil ends

2. A tool for removing insulation from the wire ends. (wire strippers or whatever, if the wires are insulated.)

Procedure

1. Remove the erasers and their metal sleeves if there are any.

2. Remove the wood from the ends of both pencils. (I like those flat carpenter's pencils because I get more surface.)

3. Fill the glass container with water.

4. Attach wires to the DC voltage source, and the other ends to the tips of the pencils. It is important to make good contact with the graphite in the pencils.

5. Punch small holes in the cardboard, and push the pencils through the holes or use some other holding devices.

6. Place the exposed tips of the pencils in the water, such that the tips are fully submerged but are not touching each other or the bottom. I used insulated wire and sealed the connections and put them upside down under collection containers.

7. Turn onthe power source and wait for a minute or so: Small bubbles should soon form on the tips of the pencils. Hydrogen bubbles will form on one tip associated with the negative battery terminal - the cathode, and oxygen from the other.

Specific things you may observe:

Electrolysis does not depend intrinsically on the generation of heat although some may be produced. Therefore, it is not subject to a fundamental thermodynamic limitation on efficiency. Therefore, electrolysis can be (and is) performed at very high efficiencies close to 100%.

If you use a Voltage less than 1.5 volts, then it will be necessary to add an electrolyte, such as a salt, acid, or base, that will disassociate into charged ions and increase the flow of electrical current.

We use carbon (in the form of graphite) because it will not dissolve into the water under the influence of the electron current - the carbon is electrically neutral.

Advanced Experimentation

First make the following measurements carefully and simultaneously:

1. Collect the hydrogen produced using a container: The container should be initially filled with water and positioned over the negative electrode, with the open end submerged and the closed end pointing upwards (such that the container is completely filled with water at the start of the experiment). Run the experiment until the water level inside the container is full of gas and matches the water surface level. At this point the pressure of the hydrogen will equal ambient pressure. Stop the experiment when this level is reached.

2. Measure the current in amps: Do this by placing an ammeter in the circuit - read the meter during the experiment to get a good idea of the average current. I would cheat and use a constant current source.

3. Time the hydrogen production.

Calculate the volume of hydrogen produced at ambient pressure. Measure the volume of the container, Make sure your answer is expressed in cubic meters. For example, if you initially calculate the volume in cubic centimeters, divide your answer by 1 million.

Now calculate the theoretical (maximum) volume of the hydrogen produced, also in cubic meters, from the other data for the current and the time, using "Faraday's First Law":

V_theoretical = (R I T t) / (F p z), where

R=8.314 Joule/(mol Kelvin),

I = current in amps,

T is the temperature in Kelvins (273 + Celsius temperature),

t = time in seconds,

F = Faraday's constant = 96485 Coulombs per mol,

p = ambient pressure = about 1 x 10⁵ pascals (one pascal = 1 Joule/meter³),

z = number of "excess" electrons = 2 (for hydrogen, H₂), 4 (if you're measuring oxygen production instead).

Finally, calculate the efficiency by comparing the volume produced to the theoretical maximum volume: Efficiency (in %) = 100 x V_produced / V_theoretical .

How Does it Work?

The chemical equation for electrolysis is:

energy (electricity) + 2 H₂O -> O₂ + 2 H₂ .

At the cathode (the negative electrode), there is a negative charge created by the battery. This means that there is an electrical pressure to push electrons into the water at this end. At the anode (the positive electrode), there is a positive charge, so that electrode would like to absorb electrons. But the water isn't a very good conductor. Instead, in order for there to be a flow of charge all the way around the circuit, water molecules near the cathode are split up into a positively charged hydrogen ion, which is symbolized as H⁺ in the diagram above (this is just the hydrogen atom without its electron, i.e. the nucleus of the hydrogen atom, which is just a single proton), and a negatively charged "hydroxide" ion, symbolized OH^-:

H₂O -> H⁺ + OH^- _.

You might have expected that H₂O would break up into an H and an OH (the same atoms but with neutral charges) instead, but this doesn't happen because the oxygen atom more strongly attracts the electron from the H - it steals it (we say the oxygen atom is more "electronegative" than hydrogen). This theft allows the resulting hydroxide ion to have a completely filled outer shell, making it more stable.

But the H⁺, which is just a naked proton, is now free to pick up an electron (symbolized e^-) from the cathode, which is trying hard to donate electrons, and become a regular, neutral hydrogen atom:

H⁺ + e^- -> H

This hydrogen atom meets another hydrogen atom and forms a hydrogen gas molecule:

H + H -> H₂,

and this molecule bubbles to the surface, and voila, we have hydrogen gas!

Meanwhile, the positive anode has caused the negatively charged hydroxide ion (OH^-) to travel across the container to the anode. When it gets to the anode, the anode removes the extra electron that the hydroxide stole from the hydrogen atom earlier, and the hydroxide ion then recombines with three other hydroxide molecules to form 1 molecule of oxygen and 2 molecules of water:

4 OH^{- _}> O₂ + 2 H₂O + 4e^-

The oxygen molecule is very stable, and bubbles to the surface.