EnGen Roadshow Demo: Hydrogen Production

How It Works

[demo]
Source: Wikipedia

We connect the electrolyser to a battery or a solar panel. The electrolyser transfers electrical energy to chemical energy by separating water molecules into hydrogen and oxygen, a process called electrolysis. At the negatively charged cathode, hydrogen ions (H+) receive electrons and become hydrogen gas (H2). At the positively charged anode, water molecules give up electrons and decompose into oxygen gas and hydrogen ion. We summarize these two chemical reactions below:

Reduction Process @ the Cathode: 2 H+ + 2e- → H2
Oxidation Process @ the Anode: 2 H2O → O2 + 4 H+ + 4e-

We collect the hydrogen gas with a balloon. Then, we show that the hydrogen gas contains a significant amount of energy by lighting it up to create an explosion.

How It Is Used Today

Hydrogen is used as a fuel to transport energy. People usually liquefy hydrogen using high pressure to reduce its volume. During combustion, hydrogen combine with oxygen to create water and releases 286 kilo-joules of energy per mole.

2 H2 + O2 → 2 H2O + 572 kJ (for two moles of hydrogen)

As an example, the space shuttle burns hydrogen and oxygen in its main engine to propel itself into space.

In addition, hydrogen can be used to generate electricity via hydrogen fuel cells. Hydrogen fuel cells contain membranes with special catalysis that can generate electric current when hydrogen is supplied on one side and oxygen on the other side. This process is similar to combustion in a sense that it also combines hydrogen and oxygen to create water, but energy is captured by the electric current in this case.

Many automakers are developing vehicles that use hydrogen as their fuel instead of gasoline. Hydrogen vehicles are much more sustainable because they have zero emissions (i.e. they only emit water as a byproduct). They do not burn hydrogen directly; however, they generate electricity using hydrogen fuel cells and power the vehicles by electric motors.

History

The concept of electrolysis has been around for centuries. In 1800, two chemists, William Nicholson and Anthony Carlisle, decomposed water into hydrogen and oxygen using electricity. Since then, hydrogen has been involved in many industrial chemical processes. The first hydrogen fuel cell prototype is built by a physicist, William Grove, in 1839. About a century later, General Electric manufactured the first commercial fuel cell system for NASA's Gemini and Apollo space capsules in 1960s. In 1970s, Pratt & Whitney Rocketdyne, an American aerospace company, built the space shuttle main engine (a.k.a RS-25) that takes in hydrogen as its primary fuel.

Projects You Can Do At Home

Take a regular nine volt battery and put it into a clear plastic cup. Pour enough tap water to cover the battery. Carefully observe the bubbles coming out of the two terminals. The bubbles coming out of the negative terminal of the battery tend to be smaller and escape more rapidly then the ones coming out of the positive terminal of the battery. This is because the negative terminal generates hydrogen gas while the positive terminal generates oxygen gas. Caution: This experiment must be performed in an open area with good air circulation. Do not breath in any of the gas that comes out of the battery. Dry the battery and discard everything after the experiment.

Additional Information

Electrolyser: www.nmsea.org/Curriculum/7_12/electrolysis/electrolysis.htm
Hydrogen fuel cells: www.hydrogen.energy.gov/pdfs/doe_h2_fuelcell_factsheet.pdf
Hydrogen economy: www1.eere.energy.gov/hydrogenandfuelcells
Hydrogen duel cell vehicles: www.fueleconomy.gov/feg/fuelcell.shtml