Virtually carbon-free hydrogen generation on the way

July 16, 2008   by Jozef Winter

To be perfectly honest we’ve not been fans of hydrogen around here, in fact we’re pretty much against it for most suggested applications. The problem with hydrogen is that today the majority of it is produced from by-products of natural gas combustion which releases CO2 into the atmosphere, among other things. Other hydrogen production methods involve the intense use of electricity (coal, LPG, or nuclear-fueled) to crack water into hydrogen and oxygen. This process is inefficient and it would be much better to just use the direct electricity to accomplish what you need. We do admit though, that hydrogen will play a great role in some niche markets, which do not have easy access to electricity or it is unfeasible, such as in shipping, aviation, and other heavy transport. Thankfully researchers from Penn State have come up with a virtually carbon-free method of producing hydrogen.

Nanotubes, which seem to on the forefront of a lot of major research lately, such as the storage of hydrogen in nanomaterials as pictured above, are part of the solution. While the scientific background of the design is quite complex, it boils down to having a two different groups of nanotubes arranged in a photoelectrochemical diode. As the sun hits the diodes, they produce about 0.25 mA per centimeter square, not a lot, but enough. It actually represents about a 0.3% photoconversion efficiency, the amount of energy captured from the light, while typical solar panels are around 10-15%. The diodes, made of titanium dioxide and cuprous oxide (the green stuff on copper), act as n-type and p-type materials, essential in solar applications.

Since the materials are cheap and abundant, the diodes are also relatively inexpensive and they are looking at electroplating to reduce the cost further. Because of the materials they are using, they are able to absorb a much broader spectrum of light than normal, from 300 to 885 nanometers, capturing both ultraviolet and visible light. As the energy hits the diodes, the water is split and the oxygen and hydrogen can be found on a specific end of the diode. The only carbon involved in the process is that of mining and manufacturing the metals used in the diodes, but it produces none during use.

While the researchers admit that 0.3% isn’t a lot, they expect to reach efficiencies of 5-10%, nowhere near current hydrogen producing efficiencies, but at the cost of free sunlight and no CO2 emissions, this could be a part of everyone’s future.

via physorg