My renewables refinery – a clean power station that floats on water, with no moving parts?

The climate and energy crisis is clearly the “next big thing” facing us. There are two major pathways we need to follow if we are to deal with it.

The first is to transition away from fossil fuels to renewable energy. The second is to reduce our emissions from fossil fuels by dealing with the CO₂. I’m working on both aspects.

For renewable energy, I’m working on hydrogen production.

If we pass an electric current through water, a process called electrolysis, we have a catalyst – we split the water molecule (H₂O) and produce hydrogen and oxygen. Water is abundant, hydrogen is a fuel we can use safely as an energy source without producing carbon, while oxygen is also safe for us.

In most models for the production of ‘green’ hydrogen, we use areas of solar panels to collect the solar energy and convert it into electricity. That electricity is stored in a battery and then that battery is connected to an electrolyser, to convert the water into hydrogen and oxygen. But for this whole process to operate you need quite expensive solar panels, you need a quite expensive battery, and you need a quite expensive electrolyser to get to an overall efficiency of about 20%-30%.

I’m a materials chemist. The work I’ve been doing is based on new functional materials called nanomaterials.

Explainer: What is nanotechnology?

In my research we are using a device that harnesses the pure energy of the Sun, without the expense of a photovoltaic, to activate a catalyst. I’m coating a device with nanomaterials so that it acts as a semiconductor catalyst. This means the whole process occurs at a pretty low cost and in an environmentally friendly way.

We have made some very exciting advances. We now have quite a mature method to produce green hydrogen.

We start with the nanomaterials used to coat the surface of the device.

Only a decade or so ago, material chemists would have to experiment with every new material one by one, which meant a lot of work. Now we have better ways: we have computational simulation methods and AI. This way we can screen materials more clearly, and then achieve it.

A single particle of the material I’m working on can come down to several nanometres in diameter. The key thing about nanomaterials is that because they’re so small, the majority of the atom is exposed on the surface of the material. Because we are talking about a hydrogenous reaction – the reaction between the solid phase, gas phase and liquid phase – there must be direct contact. This means that only the atoms exposed on the surface can react – if they’re hidden underneath, they’re useless to us.

The best catalytic materials on the periodic table are always noble metals. But one of the purposes of our research is to adjust the surface chemistry and nanomorphology of these materials. We try to replace the noble metal with some non-noble metal – transition metals like nickel, iron, or cobalt, something like that. And we can even replace the transition metal with some non-metals, like carbon-based materials.

What we then get as a product in the lab are powders, which we test. That’s the first step.

The second step is to equip these powdery materials in a prototype of an electrolyser or photolyser. It doesn’t have to be a big size for us, say 10cm by 10cm. This stage will involve some kind of smart engineering – it’s not just chemistry.

In the third phase, the goal is to put them into a micro pilot plant and scale up the device.

The good thing about these prototypes is that they are module-based. If, for example, we were in a traditional power station and we wanted to scale a technology up, we would have to build a huge single reactor, which would be very costly and also full of safety risks. But when it comes to renewable energy devices, such as solar panels, you don’t need to build a single big size. You can build a small one, then replicate it, then just connect them together. It’s another one of the key advantages of renewable energy devices.

Our reactor simply floats on the surface of water – it could be seawater or even wastewater. But it can directly utilise solar energy and convert it into chemical energy, splitting the water into hydrogen and oxygen.

It’s just one device – a photocatalyst. We don’t need a battery or solar panel or electrolyser, just one floatable device. It makes it a quite straightforward method, and quite cost-effective.

It includes a really simple design to collect water from the bottom and generate hydrogen gas from the nano-catalyst surface that can be delivered to the outside of the device.

We are in the process of filing a patent on it.

If, for example, we were in a traditional power station and we wanted to scale a technology up, we would have to build a huge single reactor, which would be very costly and also full of safety risks. But when it comes to renewable energy devices, such as solar panels, you don’t need to build a single big size.

I have to say that the TRL (Technology Readiness Level) is currently not that high – the efficiency is probably under 10%. But the device is quite cost-effective, and I think it is full of potential.

In terms of the traditional energy, fossil fuels, the main challenge now is the emissions from heavy industry. I think that even in the very long term, we are still going to rely on fossil fuels to some extent. So we have to deal with those emissions.

This part of my research focuses on dealing with these large amounts of CO₂. It would be a very big thing to convert the exhaust from fossil fuels into something valuable.

What I do is use a functional material and solar energy as the catalyst to convert those CO₂ emissions into something useful – or, as we call it, CO₂ upgrading.

When we convert CO₂ into carbon monoxide, we produce a fuel we can burn. We can also convert CO₂ into methane, CH₄, which is a value-added chemical. Or if we can do an even better job, we can even convert it to methanol, ethanol, or even aviation fuels – it depends on the efficiency of the catalyst.

Put these two fields together and I call my research a “renewables refinery”. I think it holds tremendous promise for the future.

As told to Graem Sims

Above: :Australian Academy of Science feature on Professor Tianyi Ma.