Skip to comments.A Wet Way to Better Burning?
Posted on 11/25/2012 8:13:42 PM PST by neverdem
Technology is always looking for ways to make it easier to be green. Now, researchers in New York state report creating a new long-lived catalyst that uses the energy in sunlight to generate hydrogen gas, a carbon-free fuel. With further improvements, the advance could lead to systems that use sunlight to split water molecules, generating a fuel that can power cars and trucks without emitting any greenhouse gases.
The idea of using sunlight to convert water into a fuel may sound fanciful. But plants do it: They capture photons of sunlight and use that energy to split water molecules into their constituents of hydrogen and oxygen ions. Pairs of hydrogen ions are then knitted together with a pair of electrons (swiped from the oxygen ions) to make hydrogen molecules (H2).
Researchers have actually mimicked this same reaction for many years, but the catalysts they use to do so have been either too expensive or too quick to break down. So the search has been on for cheaper, more rugged catalysts.
To do the job, researchers usually look for two key ingredients: a good light absorber and a good catalyst. The light absorber captures photons of sunlight and then harnesses the energy to generate the energetic electrons. Those energized electrons are then passed to the catalyst, which knits the hydrogen ions into H2.
One hunting ground for good light absorbers has been semiconducting nanoparticles. But to date, when combined with catalysts, nanoparticles have managed to carry out their reactions at only modest speeds, too slow for full-scale industrial needs. One stumbling block is that semiconducting nanocrystals aren't typically soluble in water. So researchers have had to dissolve the nanocrystals into organic solvents, which prevent the crystals from interacting with the catalysts.
In the current study, reported online today in Science, researchers at the University of Rochester led by chemists Richard Eisenberg and Todd Krauss coated cadmium selenide nanoparticles with short organic chainlike molecules, abbreviated DHLA. This coating of DHLA chains allowed the nanoparticles to dissolve in water. And the individual chains were so short that they allowed the catalyst's nickel ions—also in the solution—to nuzzle close enough to the nanoparticles to grab the electrons and knit H2 molecules together. The Rochester team found that the catalysts were not only fast actors, knitting as many as 7000 H2 molecules every hour, but kept doing so for weeks on end without falling apart—a major advance over other H2-knitting catalysts.
Daniel DuBois, a chemist and hydrogen catalyst designer recently retired from the Pacific Northwest National Laboratory in Richland, Washington, calls the new work "a very nice contribution to the area" and says he's particularly impressed with the catalyst's durability.
Even so, the new light harvester-catalyst combo isn't quite ready for the real world. For their current experiment, the Rochester researchers didn't actually split water molecules to generate their hydrogen ions. Rather, they added vitamin C, which readily gives up hydrogen, to their solution. So the Rochester group still needs to show that their H2-making compounds will carry out the same reaction using water. If they do, they may give plants a run for their money in green technology.
Might get better results if they did their sunlight tests somewhere other than one of the cloudiest cities in the country.
Except water vapor, which is THE WORST POSSIBLE GREENHOUSE GAS OF ALL!!!!.....
Shush, you’ll alert the ecoweenies!
Vitamin C doping the water? An interesting curiosity but so what?
When I tell my ecofreak friends that, they get perturbed...
“7000 H2 molecules every hour”
If I remember correctly, Avagadro’s number is 6.02 x 10^23 and the molecular weight of molecular hydrogen is 2.
So IIRC, it takes 9,800,000,000,000,000 years with this apparatus to make 2 grams of hydrogen.
When combusted, 2 grams of hydrogen would yield about 219 Btus, which is not enough to boil a gallon of water.
Doesn’t seem too impressive to me.
This is still basic research. Wait till they get this perfected and scale up the surface area. Then it's free energy that can be compressed into tanks.
Catalyst chemistry is still a work in progress. The platinum used in a car's catalytic converter adds thousands of bucks to the cost, IIRC. Platinum and palladium are used in many industrial catalysts. The costs of many products can decrease if they can replace such expensive catalysts.
The Di-Hydrogen Oxide scare. I remember it well.
By my quick calculation, the process would have to be scaled up by a factor of 860 million billion billion to get one kilogram of hydrogen. Sounds like a challenge. When they put together a processing plant big enough to provide hydrogen to drive a single two passenger vehicle 100 miles every day - then they get to brag.....unless that 100 miles costs them more than my current commute.
The words "capture", "harness", "nuzzle", "grab", and "knit" aren't in my scientific dictionary.It makes me wonder what this article is really about. Witchcraft?
Homogeneous systems for light-driven reduction of protons to H2 typically suffer from short lifetimes because of decomposition of the light-absorbing molecule. We report a robust and highly active system for solar hydrogen generation in water that uses CdSe nanocrystals capped with dihydrolipoic acid (DHLA) as the light absorber and a soluble Ni2+-DHLA catalyst for proton reduction with ascorbic acid as an electron donor at pH 4.5, which gives >600,000 turnovers. Under appropriate conditions, the precious-metal-free system has undiminished activity for at least 360 hours under illumination at 520 nm and achieves quantum yields in water of over 36%.
You could have clicked the link to read the abstract.
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