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U Tokyo team demonstrates H2 production by steam electrolysis in SAECs at intermediate temps

A team at the University of Tokyo has demonstrated steam electrolysis using a solid acid electrolysis cell (SAEC) for the production of hydrogen. The SAEC used a CsH2PO4/SiP2O7 composite electrolyte and Pt/C electrodes; hydrogen production was successfully demonstrated with Faraday efficiencies around 80%. Their paper appears in the journal ChemSusChem.

According to thermodynamics, enthalpy change of the water electrolysis reaction (H2O → H2 + ½O2) can be written as ΔH = ΔG + TΔS, where H, G, S, T are enthalpy, Gibbs free energy, entropy, and temperature, respectively. This tells us that the total energy demand (ΔH) can be satisfied by electrical energy (ΔG) and heat (TΔS). ΔG decreases with the temperature while ΔH slightly increases. This means that the electric power required for the electrolysis becomes smaller at higher temperatures.

Solid Oxide electrolysis is conducted at > 600°C using oxide ion-conducting solid oxide electrolytes. Based on the thermodynamic consideration, solid oxide electrolysis can provide the highest conversion efficiency from electricity to hydrogen if appropriate heat sources are available. However, the high temperature leads to fast degradation of the cells and is not suitable for quick start-up and shutdown. Thus, solid oxide electrolysis at relatively low temperatures are also examined. For example, utilization of proton-conducting solid oxide electrolytes may lower the operation temperature to 400-600 °C.

The abovementioned status of the electrolysis research indicates the need for electrolysis technologies feasible in the intermediate temperature range (100-600 °C). The intermediate temperature range has potential for both the small cell overpotentials and the flexible operability suitable for the utilization of renewable energy resources. Here, we focus on an emerging intermediate-temperature electrolysis method, which is called solid acid electrolysis. Solid acid electrolysis is performed at around 200 °C by employing proton-conducting solid acids as electrolytes.

—Fujiwara et al.

In their study, the researchers found that the cell voltage under a constant current load increased with time. The performance degradation was more severe at higher temperatures.

SEM-EDX measurements showed that a certain part of the electrolyte migrated into the porous anode layer during the operation, filling the anode pores and preventing gas diffusion. It was suggested that the surface of the Pt/C catalyst in the anode was partially covered by the migrated electrolyte and became electrochemically inactive.

The team also found that the carbonaceous materials in the anode, primarily the carbon support of the Pt/C catalyst, was oxidized to carbon dioxide. The oxidation of carbon can decrease the number of electrochemically active sites in the anode. The researchers said that these phenomena were the possible causes of the performance degradation of the SAEC.

To mitigate the problems relating to the Pt/C anode, the team used a Pt mesh as an alternative anode. With a constant current load of 10 mA cm-2, the cell voltage at 220°C was almost unchanged at around -2 V for 48 h.

The superior stability of the Pt mesh anode demonstrated the importance of the anode design. Future investigations for durable and practical SAECs should focus on the control of the electrolyte migration and the development of cost-effective anodes with high oxygen evolution activity.

—Fujiwara et al.


  • Fujiwara, N., Nagase, H., Tada, S. and Kikuchi, R. (2020), “Hydrogen Production by Steam Electrolysis in Solid Acid Electrolysis Cells.” ChemSusChem. Accepted Author Manuscript. doi: 10.1002/cssc.202002281



We'll be up to our necks in H2 before the decade is out if this goes on.
I hope we can figure ways of storing and transporting it without too much energy loss.


No need to store, transport nor pipe if you make H2 where you use it.



If you are up to you neck in liquid H2, you have been flash frozen so no further problems. If you are up to neck in H2 and there is no ceiling, hold you breath for a few second and avoid ignition sources and it will rapidly dissipate. If you up to you neck with a ceiling, the hydrogen is concentrated above you so get down and try to crawl away.

But this article would not make me fear being up to my neck in hydrogen. This is just another academic research paper and not any great break through that promises a cheap, efficient source of "green hydrogen". My question would be where do they get the heat and electricity not that it makes any difference.


What strikes me is will they run these on unused renewables only, or will they expect to run them 24/7 (or whenever the wind is blowing or the sun is shining).
If you only use overflow power, the electricity should be very cheap, but you might only get a few hours / day of free power, thus your capital costs will be very high (per Kg H2)
If you run them whenever the wind is blowing, you'll have to build extra wind turbines (or solar), so you will be using power that other people could use, so you'll have high fuel costs (given that these seem to expect free electricity).
So no good solution.

Thomas Pedersen


From a purely systemic point of view, it would be important to not produce hydrogen during times of low production - that is if the plant is connected to the grid.

What is found, almost universally (depending on local rules and regulations), is that hydrogen production needs to be connected 'behind the meter' to avoid paying grid fees that could nearly double the effective cost of the hydrogen when using very cheap wind or solar power. This means that it is rarely economically feasible to produce the hydrogen where it is needed.

You could envision installing a 50 MW power export line and 150 MW electrolysis for a 200 MW wind or solar plant. When electricity prices are high, which is when the grid is power deficient, you would utilize the power line as much as possible, which would also generate more income than producing hydrogen - unless there were other commercial limitations. If not, power deficiency would lead to consumption of hydrogen to generate electricity at the same time as electricity is converted to hydrogen, which should obviously be avoided if at all possible.

The importance of a hydrogen grid with some storage caverns (the grid becomes a storage volume in itself) cannot be overstated. It is this storage which de-couples production and consumption of energy from renewable sources. When you can use hydrogen produces last week or last month then there are truly no time constraints to produce either power or hydrogen at the most opportune times. Furthermore, transmission of hydrogen in pipes rather than containers is order(s) of magnitude cheaper unless the volume is very low and distances very high.

For remote locations, transmission of large amount (>2-5 GW) of renewable energy (e.g. from North Africa to Europe) is a lot cheaper as hydrogen than as electricity. And hydrogen pipes are more easily placed underground than electrical transmission lines, something that is equally important in Europe. Nobody wants to stare at transmission lines transporting electricity from far away to someone else equally far away - if at all.


H2 has not proven to be practical for ground transportation because it takes so much energy to create and store it.


@thomas, good points.
@Lad, yes, it is expensive to create and store, but you may as well do "something" with excess renewables, and creating H2 is one of the candidates.
If anyone comes up with an all round better candidate, they will make a fortune (or someone else will if they don't protect their IP properly).

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