“Bionic leaf could provide starch, drugs... anything in a renewable way”

09/07/2017

Harvard researcher Daniel Nocera has developed a bionic leaf which imitates photosynthesis, provides hydrogen, liquid fuel and fertilisers thanks to the sun, water and bacteria. Nocera participated in the 36th Biennial Meeting of the Spanish Chemistry Society, organised by the UAB and celebrated in Sitges at the end of June.
 
What is the advantage of producing hydrogen from your artificial leaf compared to other methods such as electrolysis or from carbon compounds?

In the artificial leaf there is an electrolysis splitting water into hydrogen and oxygen, but we do it directly (vs. indirectly). Indirectly you take a solar panel, and then you have wires to catalyse, and then you do electrolysis. In the artificial leaf, the catalysts coats the silicon on the solar cell and there are no wires. So an advantage of the artificial leaf is that it is much more simple to fabricate, because it is only coatings and silicon. You can think of a glass, and then you have a coating on a glass. You have silicon with just coatings, so that’s easier to manufacture, because we know how to do coatings very easily.

With regard to the other part of the question, which is carbon, the problem always is that you make CO2. Whenever you try to get hydrogen out of anything that contains carbon, inevitably you will generate CO2. If people are worried about climate change you have to avoid that.

Is it better to obtain hydrogen from the sun than to get electricity with photovoltaic panels?

Yes. When you have solar panels, that is fine, but you can only get the electricity when the sun is there. When the sun goes down you do not have it anymore. The water splitting gives you a mechanism to store the solar energy because when the sun is heating the solar panel you are generating electricity and you can store it in hydrogen and oxygen. Then, later at night, when the sun goes down, you can recombine the hydrogen and oxygen in a fuel cell and get the electricity back on demand. The artificial leaf gives you a method for storing the energy. Without that, you can only use a solar panel when the sunlight is there.

You have also developed a leaf that produces fertilizers. How does it work?

We did two things. With one of them we can make fertilizers, and with the other version we can make liquid fuel. They both work the same way, only the details are different. We use the artificial leaf that splits water into hydrogen and oxygen, and you could use hydrogen as a fuel in a fuel cell. But the infrastructure is not set up to use hydrogen. So what we do is we take bacteria and we genetically engineer them to bring the hydrogen in, from the artificial leaf. One bacteria can bring nitrogen in from the air, it takes the hydrogen from the artificial leaf, and inside the bacteria it combines the hydrogen with the nitrogen to make ammonia or solid nitrogen biomass, and you can use that for direct fertilisation of crops. So it’s totally renewable. You are just using sunlight + water. That makes renewable hydrogen. And then it takes nitrogen from the air + the hydrogen, and makes fertilizer.

In another version, we do the same thing, but it does not take in nitrogen, it takes in carbon dioxide from the atmosphere. It combines it with hydrogen and makes liquid fuel. We call this combination a hybrid of putting biology and interfacing it with inorganic energy chemistry. And these hybrid systems have a lot of power associated with them.
 
Were you looking for these results or were you searching for something else?

I started this research when I was 25, just to split water into hydrogen and oxygen. That took a long time because we had to invent different fields of science. We needed to figure out what is now called “proton coupled to electron transfer” - how electrons and protons are coupled to each other. It took many years to figure out this dance between electrons and protons. Once we figured that out, we then set out to make catalysts to take advantage of everything we learnt about electrons and protons; in other words, to make a catalyst to split water into hydrogen and oxygen. Then it was logical to make the artificial leaf interface with silicon and, then, only a few years ago, we asked ourselves how could we get the hydrogen into a bigger product, so that’s when we came up with bacteria. That has been a sort of life goal since I started doing science at 25 years old.
 
You founded a start-up to develop this research and bring it into the market, in India...

I have two start-ups. We have a company called SunCatalytix that developed the flow battery. It is a big battery you could have at the power company, then the solar panels on your roof generate electricity that you could send back over the grid to the power company, they could store it for you and, at night, give it back to you. To do that, you need this thing called the flow battery which we invented. Lockheed Martin bought it and they are commercializing it.

With the artificial leaf, in its newer version, which we call the bionic leaf, I’m going to do it differently. I’m going to develop it in India. So I’m not going to do a start-up in America and then try to sell it in India. We are passing all of our knowledge over to India and I’m working with an institute there, the Institute of Chemical Technology, in Mumbai. And they are going to do the scale up and prototyping, and then, Indian investors will work with Indian scientists and engineers to develop it and then roll it out. I will not start a formal company to do that. I’m going to let the Indians do that. I’m going to give them the knowledge we have to help them do that.

What is the goal of this?

The goal is slightly different. In the developed world, like in Spain, you have a big infrastructure already. You can do fertilization, you have a big chemical industry to do fuels for you, but if you’re in the developing world they haven’t built that infrastructure yet. Rather than have them build that infrastructure, the question is, would they choose a different path and create a more delocalised infrastructure. The goal is to make it affordable, but it’s an easy price target to hit, because in Spain you put the infrastructure in place and you have already paid it off. In India, rural China, Africa, etc. they have to build that infrastructure, which is going to cost a lot of money. The question is, rather than doing that, can we use the money to do this more distributed renewable energy platform. That’s what I am hoping will be able to be competitive in that market with these discoveries and make it affordable for people.

Do you have any partners for the project here, in Europe?

I do not have any partners in Europe who I have been working with, but I do have a lot of friends. As scientists we always play off of each other’s research. But in terms of commercialization strategies, no, that’s all being done in India. I’m not even doing it in America, actually.

What are your future plans, are you working on any other technologies?

With the bionic leaf we have renewable hydrogen, that powers bacteria, and we make fertilizer and liquid fuel. But genetically, I could encode the bacteria to make anything. They could make starch, or they could make drugs. What are your future plans, are you working on any other technologies? With the bionic leaf we have renewable hydrogen, that powers bacteria, and we make fertilizer and liquid fuel. But genetically, I could encode the bacteria to make anything. They could make starch, or they could make drugs. In a more general way, this is a way to make the chemical industry renewable, using sunlight and water. We would like to generalise this to make it simply a renewable chemical platform, because depending on what genetics I put into the bug, it eats the hydrogen, and I can in principle have it make anything. That’s what we are thinking about right now.