Jul
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A New Method to Extract Hydrogen Everywhere
July 30, 2008 | 2 Comments
I don’t spend much time on hydrogen production methods, as they are so far stunningly expensive even though some new ones are very efficient. One thing is certain; humanity will need free hydrogen to make good use of the planet’s resources and work responsibly with the carbon cycle. Another point made to me about hydrogen is that letting H or H2 out into the atmosphere isn’t a great idea. One, being the planet’s systems expect H to be locked up with oxygen or involved with carbon and many times both. Second is the free hydrogen really will just rise into the upper atmosphere and be blown off by the solar wind if not combined with the ozone. Earth’s mass will be reduced, gone forever.
This brings us to the latest innovation in splitting water. Professor Craig A. Grimes at Penn State has a new process that uses light for power. While I’ve seen proposals before, Professor Grime’s method isn’t stunningly expensive. It is not especially efficient, but it looks affordable.
The clever innovation is a “photoelectrochemical” diode that does a “photolysis” of water. New words now. The diode part comes from the light entering on one side, doing one part of the job, continuing across the substrate and energizing the other side to do the other part of the job, a one way only process. A light wave thus stimulates the light facing side, which is titanium dioxide with a doping of iron soaking up the ultraviolet light in the 300-to 400-nanometer range. Passing over to the other side the light in the 400 to 885 nanometer range energizes the copper titanium side. The two materials thus use the full spectrum of the light segment of the electromagnetic spectrum.
The titanium dioxide layer produces oxygen and the copper titanium layer produces hydrogen. Very neat indeed. So when you hear its only 0.30% efficient one isn’t so disappointed as it’s from a very wide range of light, it’s a first effort, and very low cost. Grimes suggests that perhaps as high as 10% efficiency is possible as no optimization has taken place. But the proof of concept works; the materials and construction offer that the devices are photo stable so lasting a very long time.
The other outstanding point is the device separates the oxygen and hydrogen in the course of operation. Grimes’ process is far more sophisticated than just the innovative materials and construction. The building up process itself is quite interesting. In Grimes’ photoelectrochemical diode, one side is a nanotube array of electron donor material – n-type material – titanium dioxide, and the other is a nanotube array that has holes that accept electrons – p-type material – cuprous oxide titanium dioxide mixture. P and n-type materials are common in the semiconductor industry. Grimes has been making n-type nanotube arrays from titanium by sputtering titanium onto a surface, anodizing the titanium with electricity to form titanium dioxide and then annealing the material to form the nanotubes as used in other solar applications. He makes the cuprous oxide titanium dioxide nanotube array in the same way and can alter the proportions of each metal.
There aren’t any graphics on the Penn State news release, nor a comment about a paper. On the other hand the U.S. Department of Energy supports the research and the team members are Gopal K. Mor, Oomman K. Varghese and Karthik Shankar, research associates; Rudeger H. T. Wilke and Sanjeev Sharma, Ph.D. candidates; Thomas J. Latempa, graduate student, all at Penn State; and Kyoung-Shin Choi, associate professor of chemistry, Purdue University.
This might all seem a little under the level of what is usually covered, but it’s a large team from Penn State. I do wish they thought to offer a little more, but its early in the research. What grabs attenteion is the low cost and the separated elements. This could be a very important development.
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I was just having a conversation over this I am glad I came across this it cleared some of the questions I had.
Hello, this is my first time i visit here. I found so many interesting in your blog especially on how to determine the topic. keep up the good work.