6 ms·

Interesting news, but it should be noted that quantum efficiency is only a part of overall efficiency. 100% quantum efficiency means that for 1 photon of suffic

by corty 6y ago

Interesting news, but it should be noted that quantum efficiency is only a part of overall efficiency. 100% quantum efficiency means that for 1 photon of sufficient energy you get 1 split H_2O. But it doesn't take into account which part of sunlight would be usable (there will be an energy cutoff) and what efficiency at channeling sunlight photons onto the catalyst your setup will have. Also, I'm missing the environmental conditions. If the process only works at >9000MPa and >9000K, it will be useless...

graderjs 6y ago
Other readers should not be discouraged by the above comment. Although it's disappointing to see this lazy skepticism as the top and longest lived comment. For a serious paper and a serious forum, I think a comment owes it to that seriousness and its readers to carefully investigate before displaying contempt. Under Methods: Photocatalytic reactions Photocatalytic reactions were carried out in an overhead-irradiation-type glass vessel connected to a closed gas circulation system. Prior to each reaction, all air was evacuated from the reaction system and filled with Ar (about 1 kPa unless otherwise noted). The suspension was subsequently irradiated using a Xe lamp (300 W, full arc). Evolved gases accumulated in the closed gas circulation system were analysed by gas chromatography (GC-8A, Shimadzu Co., thermal conductivity detector, Ar carrier gas, molecular sieve 5 Å column). The STH efficiency was measured under simulated sunlight irradiation (AM1.5G, 9 cm2 illuminated area, solar simulator HAL-320, Asahi Spectra Co.). The STH efficiency was determined according to the following equation We can clearly see it is 1 atmosphere, and reasonably assume it's "ambient temperature" plus 300 W Xe lamp irradiation. And it mentions nothing about "sunlight" but we can get consider the light spectra from the lamp. Comments should in future refrain from being inaccurate and lazily put together like the above. I think this goes doubly so for revolutionary and energy type tech that can be radically transformative. Good comments should push brave new science into the light, not drag it down into the dark of existing confirmation bias.
- antonvs 6y ago
  The comment you replied to did not "display contempt." It pointed out a caveat for quantum efficiency, and that the linked article did not mention the environmental conditions. You could have contributed constructively, but you chose instead to bring down the tone. It is your comment that is not appropriate to a "serious forum."
  - chrisweekly 6y ago
    But the linked article did mention environmental conditions, justifying the "lazy" criticism.
    - wizzwizz4 6y ago
      But you did bring down the tone in an otherwise excellent comment. Assume good faith, please.
      - rat9988 6y ago
        I assume it was in good faith and that he didn't read the article. Lazy and good fatih aren't in odd.
  - mootzville 6y ago
    Commenting on another commenters comments as "bringing down the tone" in regards to their comments about another commenters comments "displaying contempt" is what really "brings down the tone" for me.
    - arcticbull 6y ago
      Thing is I at least didn’t see the top post as bringing down the tone. They posited questions as folks here do and added to the topic. I for one would not have even known what to ask without the top comment. You assumed a lot of negativity and bad intent from the person and what they wrote that I didn’t see. HN isn’t meant to be a cheer squad for anything new, IMO. It’s meant to be a forum for folks to discuss and people will have differing reactions but so long as they add something interesting, the comments are welcome, again IMO.
- rattray 6y ago
  Thank you for sharing some of the environmental conditions of the test. I do remain curious how this might generalize to real-world efficiency...
- cheschire 6y ago
  I have been chastised (rightly so) by dang for name-calling when referring to someone's pedantry. I resisted at first because I did not call the person pedantic, merely referenced their pedantry. In this same way I see your wording as calling the GP "lazy" even though you did not use the specific grammatical form. If your post is not too old by the time you see this, I suggest finding another way to word your message to get the same point across.
  - vendiddy 6y ago
    I think deleting the word lazy, deleting the 2nd paragraph, and deleting the 2nd part of the last paragraph would get the same point across.
    - graderjs 6y ago
      I will certainly respond to this, however, I'm unable right now as I'm drinking a beer.
      - graderjs 6y ago
        Okay, let me try your edit (deleting the word lazy, deleting the 2nd paragraph, and deleting the 2nd part of the last paragraph), and discuss below: Other readers should not be discouraged by the above comment. Although it's disappointing to see this skepticism as the top and longest lived comment. Under Methods: Photocatalytic reactions Photocatalytic reactions were carried out in an overhead-irradiation-type glass vessel connected to a closed gas circulation system. Prior to each reaction, all air was evacuated from the reaction system and filled with Ar (about 1 kPa unless otherwise noted). The suspension was subsequently irradiated using a Xe lamp (300 W, full arc). Evolved gases accumulated in the closed gas circulation system were analysed by gas chromatography (GC-8A, Shimadzu Co., thermal conductivity detector, Ar carrier gas, molecular sieve 5 Å column). The STH efficiency was measured under simulated sunlight irradiation (AM1.5G, 9 cm2 illuminated area, solar simulator HAL-320, Asahi Spectra Co.). The STH efficiency was determined according to the following equation We can clearly see it is 1 atmosphere, and reasonably assume it's "ambient temperature" plus 300 W Xe lamp irradiation. And it mentions nothing about "sunlight" but we can get consider the light spectra from the lamp. It's still very good, I grant you that. But i don't think it's as excellent as the original. The reasons are i think it's important to point out what good comments should do and to point out the damage done by laziness of making authoritative sounding comments that don't accurately reflect and in fact misrepresent the subject of their commentary, and to accurately locate the comment in its proper context in this case and accurately describe what the comment is doing which is showing contempt. I think these extra bits of information add to the accurate description of such types of comments, help people see the reasons why such comments are unhelpful to readers, are unworthy of their subject, and have no place on a serious forum. So i think the original is better suited to accomplish these various purposes than you edits.
- adrian_b 6y ago
  Actually that comment was justified, because the article says that while the quantum efficiency is around 96%, the water splitting worked with ultraviolet light having wavelengths between 350 nm and 360 nm. Only a very small fraction of the solar light is ultraviolet light, so the usable efficiency of such a device is quite low. While this research result is very interesting as a demonstration of what can be done, it is very unlikely that this is a path that can lead to the best way of capturing solar energy. Either multijunction photovoltaic cells or thermal devices can capture around half of the total solar energy. If splitting water is desired, that problem can be solved separately, using electrical or thermal energy, and it should be able to reach similarly high efficiencies as with these photocatalysts. The combined efficiency of the 2 processes should be still far greater than the efficiency of direct water splitting, which is constrained by the lack of enough ultraviolet light in the solar spectrum.
  - jjcm 6y ago
    Is the wavelength restriction a blocker though? There's already use of quantum dot film to shift light wavelengths into spectrums more suitable for growing plants[1]. Theoretically shouldn't this be able to be used to shift a larger percentage of the light spectrum into the 350-360nm range, resulting in a far higher actual yield? [1] https://ubigro.com/ https://ubigro.com/
    - adrian_b 6y ago
      Your example converts high-energy light (ultraviolet or blue) to low energy light (red). This process is easy and it can be done with quantum dots, as you say. The reverse process of converting red light to ultraviolet light, as it would be needed for this water splitting, is far more difficult and it has much lower efficiencies, especially when the input light has a low intensity. (The common green-light pointers convert infrared to green, but that works because the input is a laser beam with high intensity, so that optical media can behave non-linearly, and it still has a low efficiency). So no, wavelength conversion would not work. The only thing that would work would be to replace their semiconductor crystal with one having a much lower bandgap, like the silicon, gallium arsenide or cadmium telluride that are used in photovoltaic devices. However any such non-oxide semiconductors would be chemically unstable in contact with the nascent oxygen, so that would still not work.
- x86_64Ubuntu 6y ago
  Where did we get 1 atmosphere/101kPa from?
- graderjs 6y ago
  Sorry the "1 atmosphere" should be "1 kPa" which is about 0.01 atmosphere. I didn't remember my chemistry units. Still, something you can get to with a normal vacuum pump in a lab.
  - deleted 6y ago
    [deleted]
thereisnospork 6y ago
It appears to be good science, but lousy engineering. To be fair to the original, the whole 'this research will save the planet shtick' is pretty much boilerplate for any paper[0]. Photocatalytic H2 production will never be practical vs even boring old solar->electricity->Water-splitting. Literal acres of catalyst and transparent plumbing are not cheap or maintenance free, never mind that a hydrogen 'farm' producing mixed hydrogen and oxygen will make the Hindenburg look like a tea candle in comparison. re the conditions: the energy cutoff appears to be at around 370nm, so it essentially operates under UV light only, at atmospheric to a few bar pressure and close enough to room temperature. [0]e.g. Every nanotechnology paper is going to claim to all but revolutionize one or more of: drug delivery, cancer treatment, materials science, or my favorite, lithium batteries. Nine times out of ten though they are just taking <insert metal> and making <insert shape>: something which is useful to know how to do, but not typically revolutionary.
mensetmanusman 6y ago
Too add: In materials research the term quantum efficiency, QE, implies that there are other efficiencies to consider. E.g. in the OELD space, it is talked about that the materials developed have near 100% QE. This is useful terminology because researchers know that there are other efficiency losses that need to be improved on, and that this one can now be considered ‘finished’ (although, some even look at other effects to try to go above efficiency ‘maximums’ that appear fixed at first glance: https://news.mit.edu/2019/increase-solar-cell-output-photon-2-electron-0703 https://news.mit.edu/2019/increase-solar-cell-output-photon-...). Note: For OLEDs, although the QE is high, the light output efficiency is not very high due to internal light guiding effects.

by corty 6y ago

graderjs 6y ago

Other readers should not be discouraged by the above comment. Although it's disappointing to see this lazy skepticism as the top and longest lived comment. For a serious paper and a serious forum, I think a comment owes it to that seriousness and its readers to carefully investigate before displaying contempt. Under Methods: Photocatalytic reactions Photocatalytic reactions were carried out in an overhead-irradiation-type glass vessel connected to a closed gas circulation system. Prior to each reaction, all air was evacuated from the reaction system and filled with Ar (about 1 kPa unless otherwise noted). The suspension was subsequently irradiated using a Xe lamp (300 W, full arc). Evolved gases accumulated in the closed gas circulation system were analysed by gas chromatography (GC-8A, Shimadzu Co., thermal conductivity detector, Ar carrier gas, molecular sieve 5 Å column). The STH efficiency was measured under simulated sunlight irradiation (AM1.5G, 9 cm2 illuminated area, solar simulator HAL-320, Asahi Spectra Co.). The STH efficiency was determined according to the following equation We can clearly see it is 1 atmosphere, and reasonably assume it's "ambient temperature" plus 300 W Xe lamp irradiation. And it mentions nothing about "sunlight" but we can get consider the light spectra from the lamp. Comments should in future refrain from being inaccurate and lazily put together like the above. I think this goes doubly so for revolutionary and energy type tech that can be radically transformative. Good comments should push brave new science into the light, not drag it down into the dark of existing confirmation bias.

antonvs 6y ago
The comment you replied to did not "display contempt." It pointed out a caveat for quantum efficiency, and that the linked article did not mention the environmental conditions. You could have contributed constructively, but you chose instead to bring down the tone. It is your comment that is not appropriate to a "serious forum."
- chrisweekly 6y ago
  But the linked article did mention environmental conditions, justifying the "lazy" criticism.
  - wizzwizz4 6y ago
    But you did bring down the tone in an otherwise excellent comment. Assume good faith, please.
    - rat9988 6y ago
      I assume it was in good faith and that he didn't read the article. Lazy and good fatih aren't in odd.
- mootzville 6y ago
  Commenting on another commenters comments as "bringing down the tone" in regards to their comments about another commenters comments "displaying contempt" is what really "brings down the tone" for me.
  - arcticbull 6y ago
    Thing is I at least didn’t see the top post as bringing down the tone. They posited questions as folks here do and added to the topic. I for one would not have even known what to ask without the top comment. You assumed a lot of negativity and bad intent from the person and what they wrote that I didn’t see. HN isn’t meant to be a cheer squad for anything new, IMO. It’s meant to be a forum for folks to discuss and people will have differing reactions but so long as they add something interesting, the comments are welcome, again IMO.
rattray 6y ago
Thank you for sharing some of the environmental conditions of the test. I do remain curious how this might generalize to real-world efficiency...
cheschire 6y ago
I have been chastised (rightly so) by dang for name-calling when referring to someone's pedantry. I resisted at first because I did not call the person pedantic, merely referenced their pedantry. In this same way I see your wording as calling the GP "lazy" even though you did not use the specific grammatical form. If your post is not too old by the time you see this, I suggest finding another way to word your message to get the same point across.
- vendiddy 6y ago
  I think deleting the word lazy, deleting the 2nd paragraph, and deleting the 2nd part of the last paragraph would get the same point across.
  - graderjs 6y ago
    I will certainly respond to this, however, I'm unable right now as I'm drinking a beer.
    - graderjs 6y ago
      Okay, let me try your edit (deleting the word lazy, deleting the 2nd paragraph, and deleting the 2nd part of the last paragraph), and discuss below: Other readers should not be discouraged by the above comment. Although it's disappointing to see this skepticism as the top and longest lived comment. Under Methods: Photocatalytic reactions Photocatalytic reactions were carried out in an overhead-irradiation-type glass vessel connected to a closed gas circulation system. Prior to each reaction, all air was evacuated from the reaction system and filled with Ar (about 1 kPa unless otherwise noted). The suspension was subsequently irradiated using a Xe lamp (300 W, full arc). Evolved gases accumulated in the closed gas circulation system were analysed by gas chromatography (GC-8A, Shimadzu Co., thermal conductivity detector, Ar carrier gas, molecular sieve 5 Å column). The STH efficiency was measured under simulated sunlight irradiation (AM1.5G, 9 cm2 illuminated area, solar simulator HAL-320, Asahi Spectra Co.). The STH efficiency was determined according to the following equation We can clearly see it is 1 atmosphere, and reasonably assume it's "ambient temperature" plus 300 W Xe lamp irradiation. And it mentions nothing about "sunlight" but we can get consider the light spectra from the lamp. It's still very good, I grant you that. But i don't think it's as excellent as the original. The reasons are i think it's important to point out what good comments should do and to point out the damage done by laziness of making authoritative sounding comments that don't accurately reflect and in fact misrepresent the subject of their commentary, and to accurately locate the comment in its proper context in this case and accurately describe what the comment is doing which is showing contempt. I think these extra bits of information add to the accurate description of such types of comments, help people see the reasons why such comments are unhelpful to readers, are unworthy of their subject, and have no place on a serious forum. So i think the original is better suited to accomplish these various purposes than you edits.
adrian_b 6y ago
Actually that comment was justified, because the article says that while the quantum efficiency is around 96%, the water splitting worked with ultraviolet light having wavelengths between 350 nm and 360 nm. Only a very small fraction of the solar light is ultraviolet light, so the usable efficiency of such a device is quite low. While this research result is very interesting as a demonstration of what can be done, it is very unlikely that this is a path that can lead to the best way of capturing solar energy. Either multijunction photovoltaic cells or thermal devices can capture around half of the total solar energy. If splitting water is desired, that problem can be solved separately, using electrical or thermal energy, and it should be able to reach similarly high efficiencies as with these photocatalysts. The combined efficiency of the 2 processes should be still far greater than the efficiency of direct water splitting, which is constrained by the lack of enough ultraviolet light in the solar spectrum.
- jjcm 6y ago
  Is the wavelength restriction a blocker though? There's already use of quantum dot film to shift light wavelengths into spectrums more suitable for growing plants[1]. Theoretically shouldn't this be able to be used to shift a larger percentage of the light spectrum into the 350-360nm range, resulting in a far higher actual yield? [1] https://ubigro.com/ https://ubigro.com/
  - adrian_b 6y ago
    Your example converts high-energy light (ultraviolet or blue) to low energy light (red). This process is easy and it can be done with quantum dots, as you say. The reverse process of converting red light to ultraviolet light, as it would be needed for this water splitting, is far more difficult and it has much lower efficiencies, especially when the input light has a low intensity. (The common green-light pointers convert infrared to green, but that works because the input is a laser beam with high intensity, so that optical media can behave non-linearly, and it still has a low efficiency). So no, wavelength conversion would not work. The only thing that would work would be to replace their semiconductor crystal with one having a much lower bandgap, like the silicon, gallium arsenide or cadmium telluride that are used in photovoltaic devices. However any such non-oxide semiconductors would be chemically unstable in contact with the nascent oxygen, so that would still not work.
x86_64Ubuntu 6y ago
Where did we get 1 atmosphere/101kPa from?
graderjs 6y ago
Sorry the "1 atmosphere" should be "1 kPa" which is about 0.01 atmosphere. I didn't remember my chemistry units. Still, something you can get to with a normal vacuum pump in a lab.
- deleted 6y ago
  [deleted]

thereisnospork 6y ago

It appears to be good science, but lousy engineering. To be fair to the original, the whole 'this research will save the planet shtick' is pretty much boilerplate for any paper[0]. Photocatalytic H2 production will never be practical vs even boring old solar->electricity->Water-splitting. Literal acres of catalyst and transparent plumbing are not cheap or maintenance free, never mind that a hydrogen 'farm' producing mixed hydrogen and oxygen will make the Hindenburg look like a tea candle in comparison. re the conditions: the energy cutoff appears to be at around 370nm, so it essentially operates under UV light only, at atmospheric to a few bar pressure and close enough to room temperature. [0]e.g. Every nanotechnology paper is going to claim to all but revolutionize one or more of: drug delivery, cancer treatment, materials science, or my favorite, lithium batteries. Nine times out of ten though they are just taking <insert metal> and making <insert shape>: something which is useful to know how to do, but not typically revolutionary.

mensetmanusman 6y ago

Too add: In materials research the term quantum efficiency, QE, implies that there are other efficiencies to consider. E.g. in the OELD space, it is talked about that the materials developed have near 100% QE. This is useful terminology because researchers know that there are other efficiency losses that need to be improved on, and that this one can now be considered ‘finished’ (although, some even look at other effects to try to go above efficiency ‘maximums’ that appear fixed at first glance: https://news.mit.edu/2019/increase-solar-cell-output-photon-2-electron-0703 https://news.mit.edu/2019/increase-solar-cell-output-photon-...). Note: For OLEDs, although the QE is high, the light output efficiency is not very high due to internal light guiding effects.