Hydrogen, storage and production: evolution and H2 technologies

[Remundo]

Note that HCOOH (-) CO2 + H2 is not a new idea for storing H2 in a derived form that is more easily manipulated.

The difficulty lies in the catalyst capable of directing the reaction in one direction or the other.

EPFL would use a form of Ruthenium, it's very technical and I admit my big shortcomings ...

On the other hand, the “CO2 absorption” aspect is not really honest since the CO2 is released during the regeneration of H2. Such a process cannot be considered as an effective carbon sink.

[Obamot]

Is it me, or the title of the thread says that the catalyst is iron? Or are we talking about something else?

Research is advancing with great strides to create methanol from Co2, there too, the catalyst is ruthenium:

http://www.futura-sciences.com/magazine ... que-55027/

Always from noble metals, but perhaps one day also simply with iron (as EPFL has managed to do in the title of this thread).

And 50% of yield, it is no longer 60% of 18% as with PV panels, there it becomes frankly interesting?

[Obamot]

H²: after its storage, the EPFL tackles its collection!

Producing hydrogen with ambient air!

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EPFL chemists have invented an artificial solar sheet, based on a new transparent and porous electrode. It can harvest atmospheric water and convert it into hydrogen. This semiconductor technology is simple to manufacture and to implement on a large scale.

12% maximum theoretical efficiency: a good start?

For decades, scientists have dreamed of a device powered entirely by solar energy to harvest water from the atmosphere and convert it into hydrogen. At EPFL, engineer and chemist Kevin Sivula has taken an important step towards realizing this concept. With his team, he developed a system as simple as it is ingenious. It combines semiconductor technologies and innovative electrodes that exhibit two key characteristics: porosity, to maximize contact with atmospheric water, and transparency, to optimize exposure to sunlight of the semiconductor coating. Under natural light, the device extracts water from the surrounding air and produces hydrogen. The results are published in Advanced Materials. https://onlinelibrary.wiley.com/doi/10. ... .202208740

Where does the innovation reside? In gas diffusion electrodes, transparent, porous and conductive. They thus allow this solar technology to transform water – present in the air in a gaseous state – into hydrogen.

"For a sustainable society, we need to find new ways to store renewable energy in a chemical form that can be used as fuel or as a raw material for industry," says lead author Kevin Sivula. from EPFL's Laboratory of Molecular Engineering of Optoelectronic Nanomaterials. Daylight is the most abundant form of renewable energy, and we are working to develop economically viable ways to produce solar fuels.”

Inspired by plant leaves
In their work for non-fossil renewable fuels, EPFL engineers, in collaboration with Toyota Motor Europe, were inspired by the ability of plants to convert daylight into chemical energy by harnessing the carbon dioxide present in the atmosphere. 'atmosphere. Basically, plants harvest CO2 and water from their environment and then, through the energy boost of sunlight, convert these molecules into sugars and starch. A process known as photosynthesis.

Designed by Kevin Sivula and his team, the transparent gas diffusion electrodes can be coated with a semiconductor material that collects light. It thus acts like a leaf, collecting light and water present in the atmosphere to produce hydrogen. Solar energy is stored in the form of hydrogen bonds.

Instead of producing electrodes in the traditional way, with opaque layers, their substrate consists of a three-dimensional mesh of glass fibres.

“It was difficult to develop our prototype, because the transparent electrodes with gas diffusion had never been the subject of a previous demonstration, explains Marina Caretti, author in charge of the study. For each step, we had to develop new procedures. But, since each step is relatively simple and easy to scale up, I believe our approach will open new horizons for a variety of applications, starting with gas diffusion substrates for solar power generation. hydrogen."

From liquid to atmospheric humidity
Kevin Sivula and other research groups have already demonstrated that artificial photosynthesis can be achieved by generating hydrogen from water and sunlight with a photoelectrochemical (PEC) cell. This cell is generally known as a device which uses incident light to stimulate a photosensitive material, for example a semiconductor, which is immersed in a liquid solution to cause a chemical reaction. From a practical point of view, the process has disadvantages. For example, it is complicated to produce large-area PEC devices that take advantage of liquid.

Kevin Sivula wanted to show that PEC technology can be adapted to harvest atmospheric humidity. This led to the development of their gas diffusion electrode. It has been shown that electrochemical cells work with gases rather than liquids. But until now, gas diffusion electrodes have been opaque and incompatible with solar PEC technology.

Scientists are now focusing on optimizing the system. What is the ideal fiber size? The perfect pore width? The best semiconductor and membrane materials? These are the questions they are pursuing as part of the European “Sun-to-X” project, dedicated to advancing this technology and developing new ways to convert hydrogen into liquid fuels.

Making Transparent Gas Diffusion Electrodes
To produce transparent gas diffusion electrodes, scientists started with a kind of glass wool. These are essentially quartz fibers (or silicon oxide), transformed into sheets of felt, by fusing them at high temperature. Afterwards, the plates are coated with a transparent film of fluorine-enhanced tin oxide. A material known for its excellent conductivity, robustness and ease of mass production. These first steps result in a transparent, porous and conductive plate, essential to maximize contact with water molecules present in the air, as well as to allow photons to pass through. The plate is covered with another coating: a thin film of semiconductor materials that absorb light. https://pubs.acs.org/doi/10.1021/jacs.0c00126
This second layer still lets light through, although it appears opaque due to the large surface area of ​​the porous substrate. As it is, the wafer can already produce hydrogen when it is exposed to the Sun.

The scientists went on to develop a small chamber that contains the plate, as well as a membrane to separate the gas produced, in order to make measurements. When the chamber is exposed to light under humid conditions, hydrogen is produced. That was the goal of the scientists. They show that it is possible to make a transparent electrode with gas diffusion to produce hydrogen from solar energy.

The scientists did not formally study the efficiency of the conversion in their demonstration. But the team agrees that it remains modest with this prototype, less than what liquid-based PEC cells are capable of. With current materials, the maximum theoretical plate efficiency for solar-hydrogen conversion is 12%, while 19% efficiency has been demonstrated for liquid-based cells.

LINK: https://actu.epfl.ch/news/produire-de-l ... r-ambiant/

Author: Hillary Sanctuary
Source: EPFL

This content is distributed under the terms of the Creative Commons CC BY-SA 4.0 license. You can freely use the texts, videos and images contained therein provided you credit the author of the work, and not restrict its use. For illustrations not containing the CC BY-SA mention, the authorization of the author is necessary.

Projects
Transparent Porous Conductive Substrates for Gas-Phase Photoelectrochemical Hydrogen Production
Marina Caretti, Elizaveta Mensi, Raluca-Ana Kessler, Linda Lazouni, Benjamin Goldman, Loï Carbone, Simon Nussbaum, Rebekah A. Wells, Hannah Johnson, Emeline Rideau, Jun-ho Yum, Kevin Sivula
https://doi.org/10.1002/adma.202208740

[sicetaitsimple]

Don't worry, it's upstream research, you need it.
The question is to know if it will be able to do better to produce hydrogen than a PV+ electrolysis system for example in particularly sunny countries, knowing that they have the same defect, which is to produce only when there is of the sun.
But the PV + electrolysis system has the advantage of also working, for example, with wind power (when there is no sun) + electrolysis...
In my opinion this is where the system is almost definitively killed regardless of its intrinsic progress .....

[Obamot]

Although I understand the meaning you want to give it ("it would seem a certain failure"... eventually according to you.) we do not understand the logic. You can't say that it's good to do fundamental research, to immediately pulverize it by comparing it with century-old technological advances (6% efficiency of PV panels at Bell in the time) and tell us "that whatever we do next we will never be able to overcome it" this theoretical model that you describe (even though you add a highly discriminating step from the point of view of system performance: electrolysis)

This is also the main advantage of the EPFL discovery: obtaining hydrogen directly (therefore primary energy directly in the state of storable gas).

Without being too mistaken, I remind you that 12% efficiency for PV was the norm for a long time (amorphous —> end of 1990) and until 2010, we were already very happy to have panels that were not too expensive, a slightly below 18%, right?

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And there from the start we already get 12%.... Wow!

[sicetaitsimple]

I didn't do any performance comparison let alone write "that whatever we did next we would never be able to overcome it" (which you put in quotes!), I talked about the load factor of such a technology, which by definition can only produce hydrogen when the sun is shining.
While a system with electrolysis can operate 24/24 with, depending on the availability of the moment, the use of electricity from solar, wind, nuclear, etc.

[Christophe]

Although I understand the meaning you want to give it ("it would seem a certain failure"... eventually according to you.) we do not understand the logic.

(...)

And there from the start we already get 12%.... Wow!

The graph is unreadable, don't you have a better definition?

[Obamot]

No se por qué, perdóname...

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[Christophe]

Thank you it's better!

It's beautiful Science ... eh zizi?

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[Christophe]

Uh it's a bit WTF isn't it?

H2, electrolysis and water stress in France: