In my never ending quest to find something of interest on the internet I stumbled upon this small story.
https://www.ornl.gov...irectly-ethanol
Jammed in below the latest salacious tales from Coronations street and which Kardashian is going to have
Wayne Rooney's love child I noticed this headline.
"Lab converts Carbon dioxide to ethanol"
I figured they were kidding but took a read anyway. Now forgive me if this has been done before, but should this not be an Euraka Moment or is this just a tempting 'it will never leave the Lab' Breakthrough?
Dav
This depends on how reliably they can synthesize the semiconductor they're using as a catalyst. Theoretically speaking there will be a nanospike arrangement that
produces a catalytic efficiency high enough to make this thing useful, but practically speaking reliably synthesizing such a catalyst is unrealistic (for now).
They talk about achieving an 83% selectivity for ethanol as a product with methane, hydrogen, and carbon monoxide as additional possible products. Production of ethanol and other hydrocarbons from reduction with copper catalysts isn't new, but reduction with selectivity this high is. Basically what's going on is the copper is still performing the reduction, but the carbon nanospikes are stabilizing the intermediates favorable to the pathway that results in ethanol as a product so that they're kinetically (not thermodynamically) preferred over other intermediates for the multitude of other possible reductions. They assume that the first intermediate in the ethanol pathway is the rate-limiter so overcoming that makes it easy for the rest of the as-yet-to-be-determined reduction mechanism to occur.
N-doped graphene is key because it modifies the electron distribution through the graphene due to electronegativity differences and impurities in the framework of the nanospikes, apparently creating an active site for the catalyst; since it's electron-poor I'm assuming one of the oxygens on CO
2 lands in it. Whatever intermediate comes next is made happy by this localized partial positive charge from the N-doped graphene.
The biggest hindrance in this whole thing, and the one thing that stuck out to me when reading the paper, is that the overpotential is ridiculous; not really an electrochemist, but to my understanding that means that on a scale necessary for a fuel cell this thing is going to put off a crap-ton of heat (bond formation is exothermic). What they've managed to do is produce something that's outrageously selective, which is great, but the thermodynamic efficiency of the catalyst itself still isn't high enough for it to be viable economically, which the authors note at the end of the paper. This can be rectified by production of a more efficient catalyst (no s#!t, I know), which might be possible if they can conclude the mechanism and then design the nanospikes to assume a favorable conformation for it to occur.
My take on it, anyway. Read the paper and found it thoroughly fascinating. Thanks for sharing.