Floating leaves are the energy of the future?

We’ve all seen leaves floating idly down a river or stream, but perhaps fewer of us have thought that these could provide a source of clean fuel. Well, perhaps not a leaf in the traditional sense, but a project, dubbed the ‘floating leaf’, has been pond-ering the use of our waterways as a location to produce hydrogen fuel. Will Tingle visited St John’s College, Cambridge to see the floating leaf, and to speak to Virgil Andrei, the paper’s co-lead author, about the potential that the project holds.

Virgil- If you look at the trends in development over the past decades in the electronics industry, you will see that people started with these types of bulky electronics - think about the first mobile phones. And then a huge technological improvement could be made by introducing modern fabrication techniques and re-naturalization. And this is how we could get thin smartphones, but we could also gain additional functionality. And this is basically what we wanted to show here. We wanted to show that we can introduce these types of modern fabrication techniques to artificial leaf production and, by doing so, we were not only able to make devices which are much more scalable and much lighter, but we also gained additional functionality. So now we have these devices that can actually float on rivers since they're so light that the bubbles of products can raise them up to the surface.

Will- This contraption that's been dubbed the 'floating leaf'. What is it? And what does it do?

Virgil- Well, this is a device which uses sunlight to convert small molecules like water and carbon dioxide into useful products like hydrogen or syngas.

Will- And how does that work?

Virgil- Well this leaf consists of two light absorbers. On one hand you have a yellow light absorber that uses blue light to produce oxygen from water. And on the hand, you have a light absorber which uses the rest of the light to reduce protons into hydrogen or CO2 into CO.

Will- There's a very clean form of energy production then?

Virgil- Yeah, this is a clean way of producing fuels. In principle, you only need sunlight and these molecules to produce your fuels.

Will- So this contraption you have in front of me, it's about the size of a coaster. I mean, how much energy output could be feasibly created from this prototype?

Virgil- Yeah. So using this type of prototype, we are able to produce several milliliters of hydrogen per hour. Right now, this is a very preliminary prototype. So you can't run much with that, but the beauty of this technology is that it's modular. So in principle, you can make an array of these leaves and then they could produce enough fuel to power an engine using a smaller remote community.

Will- And how cost effective would you say that this is right now?

Virgil- One of the main advantages of this leaf is that as compared to other technologies it uses a very small amount of material. We used a flexible, lightweight, thin substrate, which means that we could decrease the amount of material that we use for these devices 15 times. And obviously if you use a much smaller amount of material that would also have an economic benefit.

Will- So obviously this is quite small, quite a prototype, but as you say there is room for expansion. What sort of scale could you see these being rolled out to?

Virgil- Yeah, so as I was saying, this technology is very modular which means, while at this moment we were able to make devices which are 10 by 10 square centimeters, nothing stops us from making an array of these devices. You can have a square meter array and then obviously you can also install several of these arrays. So you could build something similar to a floating solar farm.

Will- And on that note. If all of this is floating, is it only confined to sort of rivers and canals where there isn't that much tidal action, or could it be rolled out to the sea? Are there any limitations on the location that they could be put?

Virgil- Well, obviously it's more convenient to place them on rivers and lakes because, as you were saying, there are less waves and less tidal movement. However, we also envisioned that these arrays could be placed somewhere near the shorelines or near remote locations like islands where you really need a remote way or a decentralized way to produce your fuels.