## Researchers at Korea University develop high-performance textile-based electrodes for watersplitting

##### 06 September 2022

Researchers at Korea University have developed high-performance, textile-based electrodes for watersplitting (WSE); the non-noblemetal-based electrodes can generate a large amount of hydrogen with low overpotentials and high operational stability. An open-access paper on their work is published in the RSC journal Energy & Environmental Science.

An electrochemical water-splitting reaction offers an effective pathway to generate hydrogen fuels and store electricity from various intermittent but renewable energy sources. Recently, substantial efforts have been devoted to fabricating high-performance and low-cost water-splitting electrodes that can generate a large amount of hydrogen fuels per unit area with low overpotentials and long-term stability under alkaline conditions. To achieve this goal, non-noble metal-based catalysts have been introduced onto porous substrates with large surface area using solution processes.

However, non-uniform coating of electrocatalysts onto porous substrates, unfavorable interfacial interactions between electrocatalysts and substrates, and/or relatively low electrical conductivity of electrocatalysts notably increased the overpotentials of electrodes, and simultaneously induced unstable operation at high current density.

To address these problems, a carbonization/interfacial assembly-driven electroplating approach was applied to highly porous silk textiles. Benefiting from the fine control of the electrocatalytic deposition on the carbonized silk fibrils, insulating silks were almost perfectly converted to high-performance water-splitting electrodes with bulk metal-like conductivity, large electrocatalytic area, extremely low overpotentials, and unprecedently high operation stability.

Our approach can provide a promising tool for developing high-performance electrodes for water electrolyzers and other electrochemical energy devices.

—Mo et al.

The team first converted silk textiles to carboxylic acid-functionalized conductive textiles using carbonization and a subsequent acid treatment. Then, they assembled amine linkers onto the conductive textiles to achieve favorable interfacial interactions with electrocatalysts.

For a hydrogen evolution reaction (HER) electrode, they electroplated nickel (Ni) onto the interface-modified textile, while to prepare an oxygen evolution reaction (OER) electrode, they additionally electroplated NiFeCo onto the Ni-electroplated textile.

Schematic illustration of the carbonization/interfacial assembly-driven electroplating approach to fabricate water-splitting electrodes. Mo et al.

These HER and OER electrodes exhibited extremely low overpotentials in alkaline media (12 mV at 10 mA cm−2 for the HER and 186 mV at 50 mA cm−2 for the OER), outperforming the conventional non-noble metal-based electrodes.

The overall-water-splitting reaction of full-cell electrodes was stably maintained at a remarkably high current density of 2000 mA cm−2 and a low cell voltage of 1.70 V.

Resources

• Jeongmin Mo, Younji Ko, Young Soo Yun, June Huh and Jinhan Cho (2022) “A carbonization/interfacial assembly-driven electroplating approach for water-splitting textile electrodes with remarkably low overpotentials and high operational stability” Energy Environ. Sci. doi: 10.1039/d2ee01510b

Can the folk here who have the technical chops explain for the rest of us, like this old ex bean-counter, what this is likely to imply for system efficiency?

In particular perhaps against the wonderfully efficient Topsoe Haldor HT electrolysis system, which hits over 90%?

https://www.greencarcongress.com/2022/09/topsoe-confirms-fid-to-build-worlds-largest-soec-electrolyzer-plant-companys-biggest-single-investme.html

As Topsoe Haldor themselves say, HT is trickier and has some cost implications, but they hope to be competitive against PEM and alkaline electrolysers due to their higher efficiency.

I should note that that is a relative issue, not an absolute inability to reduce costs, as all the technologies are very rapidly reducing cost, as they are right at the start of the s-curve for taking cost out by increased volume as well as any technical improvement they manage and production 'learnings'.

Efficiency is not the be-all and end-all, as solar and wind continue to drop in cost, and deployment ramps, so from being a limited resource, renewables are on the cusp of being cheap and plentiful.

But it sure helps.

Anyone?

Dear Davemart
Complicated to answer but ball park at least 5% but could be as much 10%
Grossly over simplifying there 4 lots of losses in an alkaline cell.
a, all the power losses from the power (AC to DC rectifiers,)
b, losses through the alkaline electrolyte so called Ohmic losses,
c, then losses at the anode and d, cathode.
This development basically only addresses these last two and they are about half the total loss.
So if total efficiency was 80% and a, power loses 2% ohmic losses 8% then the anode and cathode losses are 5% each.
If you reduce c&d losses by half efficiency improved by 5% overall.
Complication is the overall economics of the electrolyser depends on how much hydrogen each square foot of anode and cathode produces. If you run them harder
(more amps / cm2)
they make more gas per square foot so the gas is cheaper albeit at lower efficiency.
So battle at moment is more about economics than efficiency. And these might be cheaper and be able to run at higher amps. So could be very good.
But all depends on how long they last.
The alkaline electrolyte is a bastard of a thing, hot and corrosive.

@SVW:

Many thanks for somewhat lightening my darkness! ;-0

I had imagined that this was more closely related to PEM electrolysers than traditional alkaline, in my ignorance, so thanks for setting me straight on that.

Presumably this means that unlike PEM, this will have limited ability to ramp up and down, so making it tougher to co-ordinate with renewables.

SOECs have the same issue, but Topsoe Haldor by the use of a modular system so that parts can be switched off have mitigated that.

' But all depends on how long they last.'

They seem to think they have covered that one:

' Furthermore, the overall WSEs maintained a low cell voltage of approximately 1.70 V even at an unprecedently high current density of 2000 mA cm−2 for long operation time (>1640 h), outperforming the non-noble metal-based WSEs reported to date. '

(ibid, introduction)

Since conventional alkaline electrolysers have an efficiency of around 70%, does a SWAG of 80% efficiency for this approach seem reasonable?

If that is the case, they may give Topsoe Haldor a run for their money on the total economics of the system, as renewables to power them are ever more economic.

Incidentally, according to this analysis when electrolysers are less than $300Kw, then they are economic even when used as little as 25% of the time, so perhaps 2000 hours out of the year: https://www.energy-transitions.org/wp-content/uploads/2021/04/ETC-Global-Hydrogen-Report.pdf ' In the past, high electrolyser costs have made it important to run electrolysers at high capacity in order to reduce capital costs per unit of production, which implied reliance on more expensive electricity from the grid. But as electrolysers capital costs fall drastically, high utilisation will no longer be crucial. As Exhibit 2.3 shows, once electrolyser costs fall below$300/kW, electricity cost becomes the almost sole driver of green production costs as long as utilisation rates are above
around 2000 hours per annum' (pg 54)

That is great for utilising renewables.

These costings are prior to the massive rises in energy costs of the last year, so even at far higher electrolyser costs than \$300KW they should be economic to run just for 2000 hours pa.

But electrolyser costs are rapidly decreasing, and will do even more with the advent of tech such as in this article.

Thanks again.

SWAG of 80% efficient?

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