Pie Pushers

Eli has to admit it, the Pielkesphere and the Breakdown Boys have nothing on the MIT Press office as Pie Pushers^{TM ER}.  There is a lot of Pie over the Cambridge sky.  In the comments, Paul K2, brings word of the latest, that has indeed metastasized across the net.  The science itself is interesting, a new, more effective, catalyst for reacting CO₂ formed by gold coating copper nanoparticles of a particular size and composition, but, of course, those remain to be optimized.  More research is needed.  The claims are ridiculous

Co-author Kimberly Hamad-Schifferli of MIT says the findings point to a potentially energy-efficient means of reducing carbon dioxide emissions from powerplants.

“You normally have to put a lot of energy into converting carbon dioxide into something useful,” says Hamad-Schifferli, an associate professor of mechanical engineering and biological engineering. “We demonstrated hybrid copper-gold nanoparticles are much more stable, and have the potential to lower the energy you need for the reaction.”

and the hopes pie in the sky high

Hamad-Schifferli acknowledges that coating industrial-scale electrodes partly with gold can get expensive. However, she says, the energy savings and the reuse potential for such electrodes may balance the initial costs.

“It’s a tradeoff,” Hamad-Schifferli says. “Gold is obviously more expensive than copper. But if it helps you get a product that’s more attractive like methane instead of carbon dioxide, and at a lower energy consumption, then it may be worth it. If you could reuse it over and over again, and the durability is higher because of the gold, that’s a check in the plus column.”

Let us temper our enthusiasm here.  It's these kinds of press releases that give public relations offices bad reps and make the S&E faculty look foolish

Did anybody ever do the thermochemistry??  If all you do is recycle methane the reaction will be thermoneutral or worse depending on the energy cost for your hydrogen (from water??  Graetzel and friends have been chasing catalysts for splitting water for decades with scientific but not economic success). 

So in a rough sketch, what is being proposed is

CO₂ + 2H₂ + catalysts---> CH₄ + O₂ + catalyst  Heat needed = 318.7 kJ/mole

Even without worrying about the energy barriers involved in breaking the CO double bonds (the catalyst lowers that, that is what catalysts do), you need a considerable amount of energy and then you burn the methane

 CH₄ + 2O₂ ---> CO₂ + 2H₂O        Heat released = -890.3 kJ/mole (the - shows it is released)

Ah, you get the energy back plus some, but you have to get the hydrogen from somewhere.  From water

2H₂O + other catalyst ---> 2H₂ + O₂    Heat needed = 571.6 kJ/mole

No problem here.  It's all free energy even though it adds up to zero net heat.  If you tell Eli you are going to get the hydrogen from biofuels, burn the biofuels, but even there, that only accounts for one cycle, which given the cost of the catalyst makes no sense.  If you are going to get it from petroleum or natural gas, to make this a cyclical process you are going to have to get your hydrogen back from the water you made.  Welcome back to zugzwang.

The only thing that CO2 cracking makes sense for is production of higher value hydrocarbons which stay buried (e.g. plastic/solvents) and fuel for motor vehicles and those have huge economic barriers as well as issues of volume.

This is press release abuse at it's worst.

Premature is a very kind description and yes, the Science Churnalists all bit.  Spread the word.

Eli will have some words later in the day for the JSC Black Knights defending their budget.