Friday, 24 October 2014
Advanced search

Atomically thin film has potential for water splitting

Researchers at North Carolina State University have shown that a one-atom thick film of molybdenum sulphide (MoS2) may work as an effective catalyst for creating hydrogen. 

Hydrogen holds promise as an energy source, but the production of hydrogen from water electrolysis currently relies in large part on the use of costly platinum catalysts.

The new research shows that MoS2 atomically thin films are effective catalysts for hydrogen production and, while not as efficient as platinum, are relatively inexpensive.

‘We found that the thickness of the thin film is very important,’ said Dr. Linyou Cao, an assistant professor of materials science and engineering at NC State and senior author of a paper describing the work. ‘A thin film consisting of a single layer of atoms was the most efficient, with every additional layer of atoms making the catalytic performance approximately five times worse.’

According to NCSU, the effect of the thin films’ thickness surprised the researchers because it has long been thought that catalysis normally takes place along the edges of the material. Because thin films have very little ‘edge,’ conventional wisdom held that thin films were essentially catalytically inactive.

But the researchers discovered that a material’s thickness is important because the thinner the MoS2 thin film is, the more conductive it becomes, thereby increasing its effectiveness as a catalyst.

‘The focus has been on creating catalysts with a large ‘edge’ side,’ Cao said in a statement. ‘Our work indicates that researchers may want to pay more attention to a catalyst’s conductivity.’

Cao developed the technique for creating high-quality MoS2 thin films at the atomic scale in 2013. The current production of hydrogen from the atomically thin film is powered by electricity. His team is working to develop a solar-powered water-splitting device that uses the MoS2 thin films to create hydrogen.

The paper, ‘Layer-dependent Electrocatalysis of MoS2 for Hydrogen Evolution,’ is published online in Nano Letters.


Readers' comments (5)

  • A many atoms thick material only has accessible atoms at the edge. Is it possible a single atom thickness material by default must have accessible atoms across its entire surface?

    Unsuitable or offensive? Report this comment

  • Thank you for your comment, JohnK. In reply, Dr. Linyou Cao at NCSU says: One main point of our work is demonstrating that a MoS2 atomically thin film with little edges can be effective catalysts for the hydrogen evolution. This is in stark contrast with the conventional wisdom of the catalytic community, which believe that only edge sites of MoS2 can be catalytically active. Unlike the conventional strategy, which looks for increasing the number of edge sites to improve the catalytic performance, our results suggest that decreasing the thickness of MoS2 materials is a key factor for efficiently catalyzing the hydrogen evolution reaction.

  • Could you help out a noob, please? How much hydrogen are we talking about? My imagination jumps to hydrogen-powered cars with this atomic film on the windscreens and a solar panel on the roof...

    Unsuitable or offensive? Report this comment

  • I would have thought that Graphene would be very suitable for this process as it is 1 atom thick and carries an electric charge.

    Unsuitable or offensive? Report this comment

  • Thanks Ed....
    Anon. Be good if it were possible, but I suspect energy in/energy out formulae may have a part to play here.

    Unsuitable or offensive? Report this comment

  • This is very interesting for 2 reasons:-

    1) Renewables can only be used effectively if we can store energy when generated and keep till demand requires it.

    And;

    2) Continuous base load power generation generates excess power at night which can be used to store energy for peak load demands.

    This technology means energy can be stored on both a macro level by commercial Generators and the National Grid and on a micro level by individuals and businesses to change the way we live and give energy security into the distant future.

    In the 1960's American 'Sun City' project undertaken to evaluate how we would live with cheap/safe nuclear fusion power it identified people did not want to heat or cook with electricity BUT preferred Gas so on a micro scale it homes within the project were fitted with electrolysis units to generate hydrogen gas for cooking and heating - I am not sure if it generated on demand or generated with off peak 'Economy7 electricity but would suggest unutilised solar power units or off peak electricity. The hydrogen could also be consumed in a hydrogen fuel cell for generating electricity during peak demand time to reduce electricity bills.

    The Sun City project also had dual fuel internal combustion engine cars running on petrol or hydrogen. The cars had a petrol tank and a water tank attached to a hydrogen tank. When plugged in to mains electricity electrolysed the water with the hydrogen pumped into the hydrogen tank - The report I saw in the 1960's on the Sun City project had the cars plugged in at night. Away from home the hydrogen tank could be filled directly with gas from a pump or from electrolysis or slot meters in parking places – Such slot meters were expected to be provided in road side cafes, diners and coffee houses or in work place car parks as in Sweden where they are provided for cars to be kept warm outside in sub- zero temperatures.
    This development has 2 advantages in the move to the Hydrogen Economy which is coming:-
    Advantage 1 – Cheap convertors for cars with negligible recycling metal value meaning they won’t become the target of theft for the platinum value.
    And;
    Advantage 2 – Cheap household convertors for household storage and use of hydrogen for cooking and heating or even generating electricity cheap electricity during peak.

    During the late 1990’s I investigated making canal and river boats using electrolysis of water when berthed to store hydrogen gas to use for cooking and heating on the boat with hydrogen fuel cell’s generating the electricity required by the boat and powering electric motors to boat. The advantages being ‘greener’ and safer boats:-
    1) Safer heating and cooking compared to propane gas in case of a leak because hydrogen is lighter than air and would rise and exit boat via vents rather than filling boats like heavier than air propane does asphyxiating sleeping occupants.
    2) No collection and return of propane cylinders and risk of leaking connections
    3) No noise from diesel engines or diesel generators
    4) No smelly diesel fume
    5) Increased space on board boat.
    Since then a number of Pleasure Craft have been built to operate on the River Thames powered by the Hydrogen Fuel Cell charged overnight when berthed.
    On a macro scale I see the future being Nuclear Power for base load generation with new nuclear builds being the interim step towards nuclear fusion and the hydrogen economy.
    On a micro scale I believe the future is still that envisaged by the Sun City project undertaken in the early 1960’s supplemented by solar panels and modern hydrogen fuel cells. Essentially the electrolysis of water on ‘off peak economy 7’ electricity and solar panels to generate hydrogen gas for cooking, heating and powering hydrogen powered cars either powered by a dual fuel internal combustion engine as the 1960’s or a modern hydrogen fuel cell.
    When the sun shines and household solar panels are producing electricity all the electricity generated should be used with any excess electricity used to generate hydrogen rather than put into the grid. At night on ‘Off Peak Economy 7’ all the electricity used should be from the grid with household hydrogen storage for heating, cooking and electricity generation should be used. At all other times electricity can be generated from the hydrogen fuel cell or taken from the grid depending upon the relative electricity prices from the grid and household generation costs from a hydrogen fuel cell. Such a system would minimise household fuel bills and motoring costs as well being green.
    Congratulations to the development team for their discoveries – I hope it can be marketed cheaply for home use ASAP.

    Unsuitable or offensive? Report this comment

Have your say

Mandatory
Mandatory
Mandatory
Mandatory

My saved stories (Empty)

You have no saved stories

Save this article