Posted on 05/14/2012 7:04:30 AM PDT by Red Badger
Hydrogen gas offers one of the most promising sustainable energy alternatives to limited fossil fuels. But traditional methods of producing pure hydrogen face significant challenges in unlocking its full potential, either by releasing harmful carbon dioxide into the atmosphere or requiring rare and expensive chemical elements such as platinum.
Now, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new electrocatalyst that addresses one of these problems by generating hydrogen gas from water cleanly and with much more affordable materials. The novel form of catalytic nickel-molybdenum-nitride – described in a paper published online May 8, 2012 in the journal Angewandte Chemie International Edition – surprised scientists with its high-performing nanosheet structure, introducing a new model for effective hydrogen catalysis.
“We wanted to design an optimal catalyst with high activity and low costs that could generate hydrogen as a high-density, clean energy source,” said Brookhaven Lab chemist Kotaro Sasaki, who first conceived the idea for this research. “We discovered this exciting compound that actually outperformed our expectations.”
Goldilocks chemistry
Water provides an ideal source of pure hydrogen – abundant and free of harmful greenhouse gas byproducts. The electrolysis of water, or splitting water (H2O) into oxygen (O2) and hydrogen (H2), requires external electricity and an efficient catalyst to break chemical bonds while shifting around protons and electrons. To justify the effort, the amount of energy put into the reaction must be as small as possible while still exceeding the minimum required by thermodynamics, a figure associated with what is called overpotential.
For a catalyst to facilitate an efficient reaction, it must combine high durability, high catalytic activity, and high surface area. The strength of an element’s bond to hydrogen determines its reaction level – too weak, and there’s no activity; too strong, and the initial activity poisons the catalyst.
“We needed to create high, stable activity by combining one non-noble element that binds hydrogen too weakly with another that binds too strongly,” said James Muckerman, the senior chemist who led the project. “The result becomes this well-balanced Goldilocks compound – just right.”
Unfortunately, the strongest traditional candidate for an electrocatlytic Goldilocks comes with a prohibitive price tag.
Problems with platinum
Platinum is the gold standard for electrocatalysis, combining low overpotential with high activity for the chemical reactions in water-splitting. But with rapidly rising costs – already hovering around $50,000 per kilogram – platinum and other noble metals discourage widespread investment.
“People love platinum, but the limited global supply not only drives up price, but casts doubts on its long-term viability,” Muckerman said. “There may not be enough of it to support a global hydrogen economy.”
In contrast, the principal metals in the new compound developed by the Brookhaven team are both abundant and cheap: $20 per kilogram for nickel and $32 per kilogram for molybdenum. Combined, that’s 1000 times less expensive than platinum. But with energy sources, performance is often a more important consideration than price.
Turning nickel into platinum
In this new catalyst, nickel takes the reactive place of platinum, but it lacks a comparable electron density. The scientists needed to identify complementary elements to make nickel a viable substitute, and they introduced metallic molybdenum to enhance its reactivity. While effective, it still couldn’t match the performance levels of platinum.
“We needed to introduce another element to alter the electronic states of the nickel-molybdenum, and we knew that nitrogen had been used for bulk materials, or objects larger than one micrometer,” said research associate Wei-Fu Chen, the paper’s lead author. “But this was difficult for nanoscale materials, with dimensions measuring billionths of a meter.”
The scientists expected the applied nitrogen to modify the structure of the nickel-molybdenum, producing discrete, sphere-like nanoparticles. But they discovered something else.
Subjecting the compound to a high-temperature ammonia environment infused the nickel-molybdenum with nitrogen, but it also transformed the particles into unexpected two-dimensional nanosheets. The nanosheet structures offer highly accessible reactive sites – consider the surface area difference between bed sheets laid out flat and those crumpled up into balls – and therefore more reaction potential.
Using a high-resolution transmission microscope in Brookhaven Lab’s Condensed Matter Physics and Materials Science Department, as well as x-ray probes at the National Synchrotron Light Source, the scientists determined the material’s 2D structure and probed its local electronic configurations.
“Despite the fact that metal nitrides have been extensively used, this is the first example of one forming a nanosheet,” Chen said. “Nitrogen made a huge difference – it expanded the lattice of nickel-molybdenum, increased its electron density, made an electronic structure approaching that of noble metals, and prevented corrosion.”
Hydrogen future
The new catalyst performs nearly as well as platinum, achieving electrocatalytic activity and stability unmatched by any other non-noble metal compounds. “The production process is both simple and scalable,” Muckerman said, “making nickel-molybdenum-nitride appropriate for wide industrial applications.”
While this catalyst does not represent a complete solution to the challenge of creating affordable hydrogen gas, it does offer a major reduction in the cost of essential equipment. The team emphasized that the breakthrough emerged through fundamental exploration, which allowed for the surprising discovery of the nanosheet structure.
“Brookhaven Lab has a very active fuel cell and electrocatalysis group,” Muckerman said. “We needed to figure out fundamental approaches that could potentially be game-changing, and that’s the spirit in which we’re doing this work. It’s about coming up with a new paradigm that will guide future research.”
Additional collaborators on this research were: Anatoly Frenkel of Yeshiva University, Nebojsa Marinkovic of the University of Delaware, and Chao Ma, Yimei Zhu and Radoslav Adzic of Brookhaven Lab.
More information: Scientific Paper: “Hydrogen-Evolution Catalysts Based on Non-Nobel Metal Nickel–Molybdenum Nitride Nanosheets”
“Ban Dihydrogen Monoxide.”
ROFLMAO!
Cute! I love it!
Cheers
so it’s still an energy losing proposition...
You had a 8” floppy on an XT? Don’t you mean 5.25”.
Did you also own a Delorean with a flux capacitor??? ;^)
It's not really a source, more like a different sort of battery. It still takes electrical energy to split the water molecule. More electrical energy than you'd get back burning the hydrogen,, or using a fuel cell to recombine the hydrogen with O2 to produced electricity, What will be the source of the electricity? Nuclear is nasty, coal is unthinkable, oil.. oops that's the problem it's supposed to be solving.
Wind that's the ticket.. Uh, no. Not enough potential energy available, and the Kennedy's won't allow it in their backyard anyway, only in yours.
Now that said, if we'd mass produce nuclear reactors, maybe using the Navy designs, it would be a good way to run your car on nuclear energy, either by burning it, or turning it back into electricity.
Yes, but you can't run the process in your car, because it takes a source of electricity. If you could generate electricity in your car, you just could just run the car on that. So you have to generate the hydrogen off vehicle, and store it on the vehicle, before it's burned or used in a fuel cell.
Yes, but you can't run the process in your car, because it takes a source of electricity. If you could generate electricity in your car, you just could just run the car on that. So you have to generate the hydrogen off vehicle, and store it on the vehicle, before it's burned or used in a fuel cell.
Yes, but you can't run the process in your car, because it takes a source of electricity. If you could generate electricity in your car, you just could just run the car on that. So you have to generate the hydrogen off vehicle, and store it on the vehicle, before it's burned or used in a fuel cell.
No that would displace the bears, or cougars, or whatever lives in the caves now.
They want us to die off.
That's because you left out the need for electricity in addition to the catalyst. However the catalyst could be used for the reaction running the other way, converting the hydrogen and oxygen back to water, and electricity.
Wow, it’s so awesomely cheap! All we have to do is retool everything including the entire transportation support infrastructure. When all that’s added in, how cheap is it? Not very.
It's just as well - reading is for sissies anywise.
—discovered to sustainably split hydrogen from water, AFreeBird wrote:
You had a 8” floppy on an XT? Don’t you mean 5.25”.—
Yes. We had 8” ones at work for whatever we were using there (other than Incoterms and Maestro keyboards, I don’t remember the names). But this one has the smaller “real” floppy.
Well, it's a little more complex than the way you put it.
Keep in mind that a catalyst doesn't execute a reaction itself, it simply acts to lower the transitional state energy "hump," thereby allowing reactions to require less energy, and therefore occur much faster than otherwise.
Also, because of the laws of thermodynamics, part of the heat energy generated by combusting the H2 will be lost as waste heat, and that's even if you could capture the rest of the heat and cycle it back into the system, which you probably can't since the system works on hydrolysis (requiring electrical energy, not just "any" old ebnergy).
—Did you also own a Delorean with a flux capacitor??? ;^)—
Oops. :-)
Actually, when I came here it was 1996 in my home universe, but 1976 here. I got them confused. ;-)
All conversions are energy losing propositions. Second law of thermodynamics. (but non thermal processes are generally much more efficient)
1st law. You can't get something for nothing. 2nd law, you can't even break even.
—However the catalyst could be used for the reaction running the other way, converting the hydrogen and oxygen back to water, and electricity.—
I just assumed that would be a peripheral function of the motor in the first place, much as a car’s motor runs the alternator.
The reason I called it similar to perpetual motion is that I would think that the hydrogen and oxygen could be converted from water vapor to water with a simple condensation coil and the electricity could be generated by the engine with, well, an alternator.
The impact is that it produces more energy than it takes in and I assume the magic happens in the catalist, producing more hydrogen/oxigen for combustion and power generation than it needs for the chemical reaction in the first place.
I still remember waiting for 20 minutes while "Tunnels of Doom" loaded from my tape drive to my TI-99 4A.
Does this process harm the bald eagle (see earlier post)?
The is the assumption, not the reality.
Catalyst only reduces the energy required for the chemical reaction to produce hydrogen and oxygen from water. It does not reverse or eliminate the need for input energy. The system is still a net loss, or rather electricity is converted to heat in the process.
TANSTAAFL
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