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Revolutionary artificial photosynthesis is getting closer

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Imagine that we could do what green plants can do: photosynthesis. We could then meet our enormous energy needs with dark green hydrogen and climate-neutral biodiesel. Scientists have been working on it for decades. Chemist Chengyu Liu will receive his doctorate on June 8 for a new step that brings artificial photosynthesis closer. He expects it to be commonplace in fifty years.

In fact, we can already do photosynthesis like green plants can. Solar energy converts CO2 and water into oxygen and chemical compounds that we can use as fuel. Hydrogen for example, but also carbon compounds such as those found in gasoline. But the costs are higher than the value of the fuel it produces. If this changes, and we can expand this artificial photosynthesis in a gigantic way, then all our energy problems will be solved. Then CO2 emissions related to energy production will become negative.

Promising, but we’re not there yet

While that sounds promising, we’re not there yet. Chengyu Liu, one of the dedicated researchers working on artificial photosynthesis: “Now that this topic is such a hot topic all over the world, I think the first real application of this will be a fact in twenty years.” But that’s not all, he continues: “After the introduction of a new technology like this, it always takes decades before it becomes common practice. The same was true after the invention of the steam engine in the 19th century. I suspect it will be another thirty to fifty years before it is used industrially on a large scale.

True green hydrogen

We already have cars running on hydrogen, with only water as the exhaust gas. But it takes a lot of energy to make that hydrogen. The “green hydrogen” we produce today only means that we get the energy to produce it from a wind turbine or a solar panel, not from coal, gas or oil. With photosynthesis, this energy comes directly from the sun, without a solar panel having to provide energy first.

No false trees, but large areas required

What would our world look like when artificial photosynthesis was the norm? Would we have artificial trees with artificial leaves everywhere to meet our energy needs? “Indeed, you need large surfaces to capture the light, CO2 gas and water (steam). This can be done, for example, in the form of solar panels on the roofs. Or we could place photosynthesis boxes in the desert, working during the day and collecting water vapor at night. There must be many more different ways to use this kind of configuration. Once we have successfully solved the problem of the price of the reactions themselves, the next step will be the optimization of the devices for large-scale applications.

Liu is already fully considering it: “It would be great if we could use seawater, because it is not rare. We would then use a device that produces energy very cheaply with free sun, free sea water and free CO2. Fossil energy would be far too expensive in comparison.

Two components: separation of water and CO2 reduction

Artificial photosynthesis, like the natural variant of green plants, consists of two parts. One is the separation of water into hydrogen and oxygen. The other is the reduction of carbon dioxide to energy-rich hydrocarbons. The objective is to realize these two parts in a single system which on the one hand reduces CO2 contents of the air, and on the other hand produces fuels and oxygen.

The ideal catalyst: effective, cheap and readily available

In his doctorate. research, Liu focused on the first part of splitting water, which produces hydrogen and oxygen. A reaction accelerator or catalyst can help make this reaction more energy efficient. Liu: “Among other things, I developed strategies to design more efficient catalysts. The ideal catalyst is not only effective, but also cheap and readily available. It shouldn’t be a rare metal, for example, that you need to get from somewhere with a lot of environmental damage.

One of the best times

Finding the ideal catalyst is one of the biggest challenges in research, Liu says. “One of the highlights of my research was when I found a new strategy to design a catalyst for the production of hydrogen, directly in a neutral pH environment.”

Liu’s research provided new design rules and ideas on how to achieve efficient artificial photosynthesis. “The results provide fundamental understanding as well as a practical strategy for finding new catalysts for water oxidation. I hope to continue my research. Eventually, I would like to be one of the researchers who realize a complete system of artificial photosynthesis.

Proponent Bonnet sees Liu being there when researchers realistically render a complete artificial photosynthesis system. “My feeling is that if people ever find a way to achieve efficient artificial photosynthesis, or a way to make an artificial leaf, Chengyu might be one of them. He has the passion, the understanding, the excellent scientific attitude and he received excellent training.

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Revolutionary artificial photosynthesis is getting closer (2022, June 1)
retrieved 2 June 2022

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