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MIT researchers significantly increase lifetimes of solid oxide fuel cells by changing pH

MIT researchers have found that changing the pH of the system can increase the lifetimes of a range of technologies including fuel cells. An open-access paper on their work is published in the RSC journal Energy & Environmental Science.

Fuel and electrolysis cells made of solid metal oxides are of interest for several reasons. For example, in the electrolysis mode, they are very efficient at converting electricity from a renewable source into a storable fuel such as hydrogen or methane that can be used in the fuel cell mode to generate electricity when the sun isn’t shining or the wind isn’t blowing. They can also be made without using costly metals like platinum.

However, their commercial viability has been hampered, in part, because they degrade over time. Metal atoms seeping from the interconnects used to construct banks of fuel/electrolysis cells slowly poison the devices.

What we’ve been able to demonstrate is that we can not only reverse that degradation, but actually enhance the performance above the initial value by controlling the acidity of the air-electrode interface.

—Harry L. Tuller, the R.P. Simmons Professor of Ceramics and Electronic Materials in MIT’s Department of Materials Science and Engineering (DMSE)

The research, initially funded by the US Department of Energy through the Office of Fossil Energy and Carbon Management’s (FECM) National Energy Technology Laboratory, should help the department meet its goal of significantly cutting the degradation rate of solid oxide fuel cells by 2035 to 2050.

A fuel/electrolysis cell has three principal parts: two electrodes (a cathode and anode) separated by an electrolyte. In the electrolysis mode, electricity from, say, the wind, can be used to generate storable fuel such as methane or hydrogen. On the other hand, in the reverse fuel cell reaction, that storable fuel can be used to create electricity when the wind isn’t blowing.

A working fuel/electrolysis cell is composed of many individual cells that are stacked together and connected by steel metal interconnects that include the element chrome to keep the metal from oxidizing. But at the high temperatures that these cells run, some of that chrome evaporates and migrates to the interface between the cathode and the electrolyte, poisoning the oxygen incorporation reaction, Tuller explains. After a certain point, the efficiency of the cell has dropped to a point where it is not worth operating any longer.

So if you can extend the life of the fuel/electrolysis cell by slowing down this process, or ideally reversing it, you could go a long way towards making it practical.

—Harry Tuller

The team showed that you can do both by controlling the acidity of the cathode surface. They also explained what is happening.

To achieve their results, the team coated the fuel/electrolysis cell cathode with lithium oxide, a compound that changes the relative acidity of the surface from being acidic to being more basic.

After adding a small amount of lithium, the researchers were able to recover the initial performance of a poisoned cell, Tuller said. When the engineers added even more lithium, the performance improved far beyond the initial value.

We saw improvements of three to four orders of magnitude in the key oxygen reduction reaction rate and attribute the change to populating the surface of the electrode with electrons needed to drive the oxygen incorporation reaction.

—Harry Tuller

The engineers went on to explain what is happening by observing the material at the nanoscale with state-of-the-art transmission electron microscopy and electron energy loss spectroscopy at MIT.nano. They found that the lithium oxide effectively dissolves the chromium to form a glassy material that no longer serves to degrade the cathode performance.

Many technologies such as solid oxide fuel cells are based on the ability of the oxide solids to breathe oxygen in and out rapidly of their crystalline structures, Tuller says. The MIT work essentially shows how to recover—and speed up—that ability by changing the surface acidity. As a result, the engineers are optimistic that the work could be applied to other technologies including, for example, sensors, catalysts, and oxygen permeation-based reactors.

The team is also exploring the effect of acidity on systems poisoned by different elements, like silica.

In addition to the DOE, this work was also funded by the National Research Foundation of Korea, the MIT Department of Materials Science and Engineering via Tuller’s appointment as the RP Simmons Professor of Ceramics and Electronic Materials, and the US Air Force Office of Scientific Research.

Resources

  • Han Gil Seo, Anna Staerz, Dennis S. Kim, Dino Klotz, Clement Nicollet, Michael Xu, James M. LeBeau and Harry L. Tuller (2022) “Reactivation of chromia poisoned oxygen exchange kinetics in mixed conducting solid oxide fuel cell electrodes by serial infiltration of lithia” Energy Environ. Sci. doi: 10.1039/D1EE03975J

Comments

Davemart

This is great news, as SOFC's/SOECs have many desirable attributes.

For instance Topsoe Haldor uses them in hydrogen production:

https://info.topsoe.com/green-hydrogen

And however enthusiastic one may be about batteries, and doubtful about the use of hydrogen, there is currently around 100 million tons of ammonia produced a year, which is set to increase a heck of a lot, and green hydrogen is needed to do that if we are to have any chance of decarbonisation, with batteries of little or no help.

Topsoe Haldor is involved in many of those giant projects to utilise solar and wind resources in the Arabian Gulf and elsewhere for such production.

So not only good news, but pretty fundamental to decarbonisation.

A lot of folk fancy SOFCs for shipping etc also.

Davemart

... and just in, Topsoe Haldor have finalised an investment decision on a 500MW, and eventually expandable to 5,000MW, SOEC in Denmark:

https://fuelcellsworks.com/news/topsoe-confirms-final-investment-decision-for-construction-of-worlds-largest-soec-electrolyzer-plant/

yoatmon

The first Fuel Cell was invented by Sir William Grove in 1838; that's just shy of two centuries. Now, if the FC is such a great invention, why was it "dormant" all this time?
I should think that for those investing financial resources in promising enterprises, it was more interesting to invest in oil than something as obscure as a "Fuel Cell".
It became of interest only after E. Musk had sparked a revolution with the introduction of a BEV.
"Peak Oil", an undeniable fact, merged into public view some two decades ago. Long before that, it was clear to anyone capable of looking beyond the tip of his nose that - sooner or later - such a point in time would be reached. With the advent of BEVs, the oil magnates searched desperately for a means to preserve their established business model. The best so far that they could resort to was the Fuel Cell. In principle, the Fuel Cell and H2 do not differ all too much from the past climate destructive means implemented from big oil; it may even be, that the adverse effects of H2 are even greater than what has been caused in the past. This will not cause sleepless nights for the top management of big oil. They didn't worry about their past activities nor will they worry about those in the future.

Davemart

@yoatman

The first batteries were about in a similar time frame, and the first battery electric cars were running over a century ago, and they got stomped by ICE.

If they are such a good idea, by your logic, then they would be universal by now.

Of course, none of that actually makes any sense, aside from the fact that neither this article nor I are talking about SOFC cars, which aren't a thing.

Davemart

@yoatman:

Please share the details of how you propose to produce ammonia for fertiliser using batteries and without hydrogen, green or otherwise.

Thanks.

yoatmon

"The first batteries were about in a similar time frame,...."
The really GREEDY always compare two or several possibilities as to which one tends to be the most successful business model; they leave it up to others to worry about the unpleasant or detrimental side effects. As long as they can get away with such procedures, they'll do it.
With the introduction of gasoline powered cars BEVs lost the comparison. It was certainly not in the interest of those who made this decision to exploit the technical possibilities of batteries. This would have necessitated financial investments in R&D. The gas hog was simply the better business model.
The rate at which battery development progresses, outdistances by far that of FCs. I'm convinced that by the time FCs reach the present functional - and price level of batteries, these will priced at a fraction of what FCs will then cost.
Cause and Effect is a universal valid principle. In accordance with this principle, most of all problems encountered from humanity have been caused by themselves. What too many individuals have not really registered is that all resources on this planet are limited. It is a known fact that we are exploiting these at a rate that bears a ill-faring future for humanity.
Too many stupid people on this planet doing or propagating stupid things. It would be a blessing for this planet and its future if the world
population would be a sane fraction of what it presently is.

yoatmon

Whilst browsing in the internet I happened to stumble across an interesting Theme: Magnetic Fusion Milestone.
MIT, in cooperation with a startup, has managed to design an electromagnet that consumes far less power while producing an unmatched powerful magnetic field. This superlative achievement constitutes an astonishing breakthrough for their deuterium / tritium fusion reactor in development. For anyone interested in the state of development of said reactor, ref. to the following link (youtube video):
https://www.youtube.com/watch?v=-KEwkWjADEA

Davemart

@yoatman:

Thanks for the link.

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