Comment by ars | Hacker News Reader

Comment by ars | Hacker News Reader

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OK, I tried. I really tried to give them the benefit of the doubt - I mean it's mit.edu, but seriously what they wrote there and what I know of physics have little to do with one another.

I fell like I'm missing a joke somewhere.

First off: what does electrolysis have to do with photosynthesis? If you want to store energy it's just as important with wind, or any other.

Second: photosynthesis and photovoltaics are not the same thing. They seem to confuse them quite a bit. And on top of that, this seems to have nothing to do with either of them - it's all about electrolysis.

Third: "Currently available electrolyzers, which split water with electricity and are often used industrially, are not suited for artificial photosynthesis because they are very expensive and require a highly basic (non-benign) environment that has little to do with the conditions under which photosynthesis operates."

Has so many errors I don't even know where to start.

a: electrolysis does not require a basic environment, it requires a salty one.

b: again mixing up photosynthesis and photovoltaics

c: there is no such a thing as artificial photosynthesis. Only plants know how to make hydrocarbons from water CO2 and light.

If someone actually did manage to create artificial photosynthesis that would be massive. Which is what I hoped to read about here, and then I didn't.

Fourth: they start off saying something about advances in solar power, and well? Where was the advance? All I see is something about electrolysis.

Fifth: "[plants] storing energy for use when the sun doesn't shine." Most plants don't actually do that. They don't store energy, they make hydrocarbons, which are not an energy source for them, they are the final product. (For us the hydrocarbon is energy storage.) There is the CAM photosynthesis cycle used by pineapples, which does actually store energy for later. But the only reason the pineapple does that is so that it doesn't dry out during the hot day, so rather it collects it's CO2 at night. This does not seem to apply here.

Someone: please tell me if I missed something massive, but this really looks like the kind of nonsense energy inventions you read about all the time. But, but, but it's on mit.edu!

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.

Thanks 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?

To 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.

Right on ars. The article brings up more questions than answers.

The reference to photosynthesis is indirect. I think the point of the reference is that photosynthesis stores the sun's energy and then uses it later on. And that is what his process will allow. Photovoltaics can provide energy all day, and instead of feeding the grid and getting energy credit the system can create hydrogen and oxygen gas and then use those later on when the sun is no longer out (through a fuel cell for example). The process, he is claiming will only presumably require water and some other "common" materials.

I imagine something like this could be possible. Some unanswered questions: How efficient is it, if it isn't efficient then can it scale? How expensive are the materials required? Where are the details? A paper, article in a magazine or even a web site with details. I have no idea why MIT would announce something like this without publishing first or simultaneously.

Links I could find:

http://web.mit.edu/chemistry/dgn/www/research/e_conversion.h...

http://web.mit.edu/chemistry/www/faculty/nocera.html

I'm not qualified (or willing to try and process all the information right now) to say if the claims in the press release are valid, but keep in mind it was written by an HR person, not a scientist or an engineer.

Unfortunately, there's no mention of a publication for this discovery, but you can read about their pior work on their webpage: http://web.mit.edu/chemistry/dgn/www/

But, but, but it's on mit.edu!

I know what you're saying and had similar thoughts. I suppressed my concerns thinking "some of this seems wrong but this is on mit.edu so they must have been through many checks".

Same lesson to be learnt as http://news.ycombinator.com/item?id=263599 ?

Yeah, I think photosynthesis doesn't come into play anywhere in the process. They're probably misusing the word to describe the generation of oxygen from water using the sunlight. I think this article gives a better summary: http://www.eetimes.com/news/latest/showArticle.jhtml?article...

No it doesn't, sunlight has nothing to do with it (using light to lyse (photolyse?) water would be cool, but they aren't). But thank you for the link, it makes more sense then the other one.

In short: as far as I can tell this invention is a new catalyst for increasing the efficiency of electrolysis.

But the catalyst is not better than current ones, it's just less toxic (and therefor cheaper). Which, while helpful, is far from groundbreaking.

The electricity can come from anywhere. Saying solar is just a buzzword to get people to click.

Correct. Furthermore, they don't even necessarily claim it's more efficient -- or at least, they don't give any numbers. It may be more efficient than electrolysis of water (that's not saying much) but is it more efficient than charging and decharging a battery?

If not more efficient, is it at least a cheaper form of energy storage? (Platinum in the catalyst suggests no, although a very thin layer might be good enough.)

In http://www.eetimes.com/news/latest/showArticle.jhtml?article..., the economics and the efficiency of this process are described: "In fact, with our catalyst almost 100 percent of the current used for electrolysis goes into making oxygen and hydrogen." This is definitely more efficient than the existing electrolysis, as the theoretical maximum efficiency of current electrolysis process is about 80%-94% (http://en.wikipedia.org/wiki/Electrolysis).

I'm not sure what you mean by whether it's more efficient than charging and discharging a battery. But the lifespan of a fuel cell is potentially indefinite and it does not require recharge(add in Oxygen and H+ any time and electricity starts to flow). Further, with each battery cycle, the efficiency of a dry cell decreases.

I think this electrolysis process can definitely make a cheaper form of energy storage than, say, batteries. Even though each anode requires small amount of Platinum, but considering the long lifespan of fuel cell storage, this form of energy storage costs much less than traditional batteries in the long run (all the toxic disposal!) And even for the purposes of propulsion, fuel cell discharge is much more efficient than internal combustion engines.

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