Artificial photosynthesis promises ‘new frontier’ of clean energy

Technology News | June 16, 2021

By Rich Pell

Materials & processes Power Management Optoelectronics Automotive Analog Energy Harvesting Batteries / Power Supplies

The process of turning sunlight directly into usable energy – i.e., photosynthesis – may soon be a feat humans are able to mimic to harness the sun’s energy for clean, storable, efficient fuel, say the researchers, potentially opening up a whole new frontier of clean energy. Such synthetic photosynthesis – the ability to store the energy easily, without requiring bulky batteries – would dramatically change the renewable energy landscape.

It would avoid the pitfalls of current clean energy technlogies such as wind turbines and photovoltaics, say the researchers, which have downsides in terms of environmental effects and complicating factors.

“We and other researchers around the world are working incredibly hard to try to come up with accessible energy,” says Yulia Puskhar, a biophysicist and professor of physics in Purdue’s College of Science. “Energy that is clean and sustainable that we can create with nontoxic, easily available elements. Our artificial photosynthesis is the way forward.”

In plants, photosynthesis is a complex set of processes where plants convert the sun’s radiance and water molecules into usable energy in the form of glucose. To do this, they use a pigment, usually chlorophyll, as well as proteins, enzymes, and metals.

Compared to photovoltaic technology, where a solar cell converts the sun’s energy into electricity, photosynthesis is radically more efficient, say the researchers. While current photovoltaic technology is only able to capture about 20% of the sun’s energy – limited by semiconductors’ ability to absorb light energy and by the cell’s ability to produce power – photosynthesis is capable of storing 60% of the sun’s energy as chemical energy in associated biomolecules.

“With artificial photosynthesis, there are not fundamental physical limitations,” says Pushkar. “You can very easily imagine a system that is 60% efficient because we already have a precedent in natural photosynthesis. And if we get very ambitious, we could even envision a system of up to 80% efficiency.”

“Photosynthesis is massively efficient when it comes to splitting water, a first step of artificial photosynthesis,” says Pushkar. “Photosystems II proteins in plants do this a thousand times a second. Blink, and it’s done.”

The researchers say they are mimicking the process by building their own artificial leaf analog that collects light and splits water molecules to generate hydrogen. Hydrogen can be used as a fuel by itself via fuel cells or be added to other fuels such as natural gas, or built into fuel cells to power everything from vehicles to houses to small electronic devices, laboratories and hospitals.

The researchers are experimenting with natural photosystem II proteins and synthetic catalysts combinations in attempts to understand what works best – and why. They say they are also putting a priority on using compounds and chemicals that are readily abundant on Earth, easily accessible and nontoxic to the planet.

Progress in artificial photosynthesis, however, is complicated, say the researchers, as photosynthesis is so multifaceted.

“The reaction is very complex,” says Pushkar. “The chemistry of splitting water molecules is extremely intricate and difficult.”

However, says Pushkar, within the next 10 to 15 years, enough progress will have been made that commercial artificial photosynthesis systems may begin to come online. For more, see “Do multinuclear 3d metal catalysts achieve O–O bond formation via radical coupling or via water nucleophilic attack? WNA leads the way in [Co₄O₄]ⁿ⁺.”