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You are correct about your first point - the connection with photosynthesis is shaky at best. This research describes a new electrocatalyst for the production
by ztravis 18y ago
You are correct about your first point - the connection with photosynthesis is shaky at best. This research describes a new electrocatalyst for the production of oxygen. The source of electrical energy for driving this production could be solar cells, but that would be just one potential use.
The paper does focus on photosynthesis, however, because the Nocera's lab works on "artificial photosynthesis," a field largely devoted to understanding the electrochemical processes of photosynthesis and mimicking them in man-made systems. For the most part, "artificial photosynthesis" focuses not on carbon fixation but on the transformation of light to electrochemical energy (via electron/proton transfer). This is the process that Nocera's research is replicating, and likely why he focuses on using solar cells as the source of energy, to parallel a plant's use of solar energy as a route to energy storage/O2 production.
Finally, I think some of your scientific analysis needs correction:
Electrolysis (in its simplest form) doesn't require any solute - it can be performed, very slowly, in pure water. Adding salt (say, NaCl), as you mention, speeds up the rate greatly. However, in doing so, the reaction changes - you'll evolve hydrogen as before, but at the anode you'll evolve chlorine gas, not oxygen. You can't use electrolysis alone to produce oxygen gas or as a route to storing energy. One alternative to this is to use an electrocatalyst, but currently, (as the article mentions), the only available catalysts require expensive metals or very basic environments (or both). This article is on the discovery of a new catalyst that will allow for the production of oxygen via catalyzed electrolysis at neutral pH and with a cheap, abundant catalyst (cobalt).
Also, if we're looking at the same quote:
"storing energy for use when the sun doesn't shine,"
the article is talking about humans storing energy, not plants. Even so, plants do store energy for when the sun doesn't shine. They metabolize hydrocarbons into ATP via mitochondria, just like we do - so glucose and other products of photosynthesis are indeed forms of stored energy.
I think a lot of the confusion stems from the fact that we're reading a popular article and not the actual research - these articles tend to pick up on terms like artificial photosynthesis, energy production, and solar energy and run with them.
- ars 18y agoThanks for the clarifications. >artificial photosynthesis" focuses not on carbon fixation but on the transformation of light to electrochemical energy (via electron/proton transfer). Then why call it photosynthesis? It's not, it's photovoltaics. If you want photosynthesis you have have to fix carbon, or you're making a mockery of the term. And if you are making hydrogen directly, then call it photolysing. Either way you are not synthesizing anything. I didn't realize that chlorine is preferred to O2, but what does it matter? I don't want O2, I want H2, and once all the chlorine is gone, won't the sodium hydroxide work just as well as NaCl? Or is that what you mean by 'very basic environment'? They should rewrite that article and omit any mention of solar, just say they invented a new cheaper way to electrolyze water. Applications include storing energy from solar or wind for when the sun isn't shining. Doesn't the above paragraph make a lot more sense than the parent article?
- ztravis 18y agoTo be honest, I don't know why it's called artificial photosynthesis versus photovoltaics - perhaps it is because this research looks to the actual chemical systems involved in photosynthesis as models for man-made systems (as opposed to trying to develop light-converting systems ab initio). In any case, "artificial photosynthesis" is commonly used to refer to research both on hydrolysis via solar energy and carbon fixation into organic compounds, both of which are fundamental to photosynthesis as a whole. I was wrong about the chlorine production, actually - it only occurs at high concentrations of salt. Otherwise (or with different solutes), you can produce oxygen. Still, I believe that this reaction is not efficient enough to be feasible as an energy source. Overall, you do want the hydrogen, but you also need an oxidant to, for example, run a fuel cell. I think there are hydrogen-chlorine fuel cells, but I imagine it would be easier and more practical to run a hydrogen-oxygen cell instead to avoid using chlorine gas/producing HCl. In any case, it boils down to developing catalysts to improve the rate and efficiency of this electrolysis (by lowering overpotentials). I agree with you that your paragraph makes a lot more sense than the parent article. It's annoying how these press releases make things seem much more revolutionary than they really are.