Carbon rejuvination not capture

by Joshaniel Cooper

Carbon capture has been widely purported to be an easy solution to one of the many global crises (the carbon dioxide one in this case). It essentially revolves around the principle that CO_2 in the atmosphere is bad so we should take it out of the atmosphere and put it somewhere else (tankers, the sea, secret underground lairs etc.) and for the most part the concept is correct. It is also a little retarded though as any CO_2 caught will eventually escape and add to the issues of a future generation (not to mention all the hassle of catching it in the first place). Fortunately help is at hand!

I recently went to a conference on electrochemistry, the last talk of the conference was by a guy called Andrew Bocarsly and was by far the most interesting talk of the conference (and I enjoy electrochemistry so the rest of them weren’t exactly boring).  His (as it turned out serendipitously discovered) solution to the issue of CO_2 storage was ingeneous- CO_2 has carbon in and fuel has carbon in so just convert the CO_2 into fuel again! The caveat is of course that this must be done whilst expending less energy (or CO_2) than getting rid of it would.

Now CO_2 conversion back to fuel is not a simple chemical process: Carbon dioxide and water, CO_2 + H_2O, goes to methanol and oxygen, CH_3OH + \tfrac{3}{2}O_2. This is a six electron transfer process which involves at least three intermediate steps, thought to be CO_2 to formic acid to formaldehyde to methanol if you want to know. Finding suitable catalysts for this process would seem to be a nightmare (ask any chemist, they would agree I think) but here is the serendipitous part: it turns out that the catalyst for every step of this process is the same and it turns out that it isn’t even platinum! (Almost all catalysts in electrochemistry are platinum it seems) Instead it is an incredibly simple organic molecule called pyradine – a benzene ring with a nitrogen in it, and thats it. Though, many other aromatic molecules work too.

Using this catalyst and a semiconducting electrode it is possible to use photoelectrochemistry (light) to drive the reaction of CO_2 to methanol (and now butanol if you get the conditions right which is technically more relevant as it is already used as a fuel). Additionally, it is even possible using only low energy photons (red etc.) so it doesn’t even need to be in space to find UV, which is nice.

Of course the research is ongoing and things may get even better (or may turn out not to be scalable), but this may well be a glimpse of the future. For further details see this paper or look up  Andrew Bocarsly (googling photoelectrochemistry carbon dioxide methanol seems to work as well).

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