Titanium carbide nanotech approach hints at hydrogen storage breakthrough
- Reference: 1610010789
- News link: https://www.theregister.co.uk/2021/01/07/hydrogen_storage_paper/
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[1]Published in Nature Nanotechnology this week, the research investigated a method using a titanium carbide alloy just a few atoms thick as a medium, which produces a "nanopump" effect to store hydrogen. The process described is about twice as effective as comparable methods.
Hydrogen is attracting interest as a green fuel, with fuel-cell cars already on the market. [2]Although breakthroughs are being made in the production of the gas , storage is a critical problem owing to the tiny size of the molecule, as Register readers [3]have been quick to point out .
Work from Professor Jianglan Shui, of the School of Materials Science and Engineering, Beihang University, and his team found that the titanium carbide material (technical name Ti 2 CT x – a type of MXene) could support 8.8wt% (hydrogen ratio) under a "relatively safe" pressure of 60 bar.
"Compared with the known room-temperature hydrogen storage materials, Ti 2 CT x shows the superiority of low-pressure hydrogen storage, which is almost double of the previously reported highest storage capacity under the same pressure," the paper said.
Meanwhile, the hydrogen release is fast and controllable, making it a "promising strategy for designing practical hydrogen storage materials."
Etch a stretch
Speaking to The Register , Professor Shui said: "At present, fuel cell vehicles use high-pressure gas cylinders to store hydrogen... however high-pressure hydrogen has limitations in storage density and safety. Existing hydrogen storage materials, such as high surface area materials (physical hydrogen) and hydrogen alloys (chemical storage), are also difficult to meet storage capacity and practical operation requirements."
He said the proposed material was made from common elements and relatively inexpensive, but required an "incomplete etching" process to partly remove layers of aluminium atoms from between the nanosheets. "In this way, the distance between sheets could be sufficiently narrow (about 0.6~0.7 nm), which is critical to the formation of [a] nanopump effect that draws hydrogen into the space between two Ti2C nanosheets," Prof Shui told us.
However, mass production of the material would have to overcome the challenges of quality control as well as stability, he said. "We will try to fix these problems in the next step. Other component materials that conform to the discovered new hydrogen storage mechanism are expected to overcome the stability problem," he said.
Meanwhile, other nanomaterials should be investigated to find out if they could harbour the properties required for effective hydrogen storage, the paper said. "We expect that this hydrogen storage approach will be applicable to a wide range of nanomaterials, especially those with plenty of sub-nanopores and chemically modifiable inner surfaces."
There will certainly be demand for more efficient hydrogen storage. The UK government alone is aiming for [4]5GW of low-carbon hydrogen production capacity by 2030 . Plans include hydrogen heating trials, aiming for a "Hydrogen Town" before the end of the 2020s.
Its green hydrogen strategy is [5]expected in the first quarter of this year .
Malte Jansen, an energy policy research associate at Imperial College London, said industry had been making commercial use of salt caverns for large-scale bulk hydrogen storage for decades. However, researchers in carbon capture storage – hoping to store CO 2 in the salt layer – were also looking to exploit these environments.
"For smaller-scale hydrogen storage, technological solutions are indeed less mature. Potential boil-off and leakage rates are of particular concern," he said.
Pressure vessels for hydrogen cars use 700 bar of pressure to store enough energy contents, which makes the process "energetically expensive" and leads to diffusion of the tiny hydrogen molecules through the metal structure or composite materials of tanks, Jansen said. This increases the necessary wall thickness and negatively impacts vehicle weight.
Another problem was the chicken-and-egg scenario facing the financing of storage projects, he said. Because there was little hydrogen production, there was not much demand for storage, "and the lack of storage makes hydrogen production harder."
"The initial costs of handling and storing hydrogen is a problem, which we will have to overcome. Ultimately, we have learned to live with fossil gas in our homes and highly flammable liquids in our vehicles. There is no reason why we cannot learn how to use hydrogen safely," Jansen said. ®
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[1] https://www.nature.com/articles/s41565-020-00818-8
[2] https://www.theregister.com/2020/11/03/greener_hydrogen_via_water_splitting/
[3] https://forums.theregister.com/forum/all/2020/11/03/greener_hydrogen_via_water_splitting/
[4] https://www.gov.uk/government/publications/the-ten-point-plan-for-a-green-industrial-revolution/title
[5] https://www.spglobal.com/platts/en/market-insights/latest-news/electric-power/102320-uk-hydrogen-strategy-to-be-launched-in-q1-itms-cooley
[6] https://whitepapers.theregister.com/
There are quite a few chemical and physical problems associated with hydrogen that mass production will never be able to solve. But, by all means, keep the subsidies research grants coming.
I hope this isn't like fusion
As in being on the edge of viability but never quite getting there. I have this vision of using solar and wind generation to electorlyse water into hydrogen that a fuel cell then turns into electricity for the auxiliary motor on my boat. There was a presentation of just this on the RI Lectures but I have this feeling that the engineering will be more challenging than thought.
I hope it works though.
Re: I hope this isn't like fusion
I think, like CCS, it's up there.
It's not just the storage
Producing hydrogen through renewables is hideously wasteful, something like 3-4x as wasteful compared to just charging the energy into a battery. That is because hydrogen must be produced from electricity, captured, stored, transported and then turned back to electricity and each step loses energy to heat etc.
That may go a long way to explain why its going nowhere as a form of vehicle propulsion - it isn't cost competitive. And while it's quicker to fill a car, you're not going to be able to charge it over night or while you do your shopping or anything like that in the forseeable future. Unless hydrogen can be produced cheaply enough from renewables that it costs less than a battery over the lifetime of a vehicle then I don't see it going anywhere.
Re: It's not just the storage
Yes, about 1/3 the efficiency overall ( 30% vs 90%). BUT: there are applications where batteries are not adequate - rail, shipping, and of course aviation. Horses for courses.
Same applies to domestic heating. It is way more energy efficient to use renewable electricity to run heat pumps, but the cost and complexity of retrofitting all existing buildings with heat pumps is pretty daunting (we have one, but we were doing a barn conversion, so starting almost from scratch). In comparison, hydrogen production from offshore wind can re-use the entire offshore oil/gas industry: rig construction, gas pipelines, etc. Domestic boilers have been required to accept up to 20% hydrogen since 1992, and there are now 100% hydrogen models available. The biggest problem is finding all the iron pipes in the network as hydrogen degrades them. So while less efficient, it is a far easier job to deliver.
For these reasons both approaches have merit and should be pursued.
Re: It's not just the storage
Yes, this: "For these reasons both approaches have merit and should be pursued"
Suspect the main issue will be keeping the debate and decision making practical and science/engineering based. Political and popular discourse is already descending to "Batteries Suck! No! Hydrogen Sucks!" and, even if you are more aware of the technicalities, some of this stuff is hard to compare.
On the face of it, sitting in a car with a steel tank of 700 Bar flammable gas sounds like a bad idea. But we happily accept sitting next to an un-pressurised tank of flammable liquid. Is that better or worse?
Similarly the first time I realised I was sitting on a battery that was being charged at >100KW I did have a brief moment of "gosh, that's like 35 kettles being on at the same time"...
Re: It's not just the storage
All true, but hydrogen overcomes the range and recharge time issues that are holding back battery electric cars. No reason why the 2 different systems can't co-exist much like Diesel/Petrol/LPG. The markets will soon establish which they prefer if not both.
Hydrogen production can be VERY cheap when produced by renewable sources during off-peak times as otherwise the lack of demand would require shutdown of those sources. Windfarm operators, especially offshore ones, do not like to have to reduce output and in the UK right now wind is 55% of renewables and rising.
Hydrogen production / storage costs are a temporary problem. Mass production will lower them mechanically.