Researchers Inch Closer to Artificial Photosynthesis

By Horace Jenkins

A team of researchers from the University of Toronto Engineering School have designed a special catalyst that should expedite an important step in artificial photosynthesis. The catalyst could use renewable energy (solar or wind power) to convert carbon dioxide into stored chemical energy, much like how plants function.

Phil De Lunda, one of the lead authors of the recent report, said, “Carbon capture technology is expensive, and solar and wind power are intermittent. You can use batteries to store energy, but a battery isn’t going to power an airplane across the Atlantic or heat a home all winter. For that, you need fuels.” He added that, “Carbon capture and renewable energy are two promising technologies, but there are problems.”

Mirroring Nature is Key

A plant’s system involves two linked chemical reactions: one splits H₂O into protons and oxygen gas and the other converts CO₂ into carbon monoxide. When that occurs, the carbon monoxide can be converted into hydrocarbon fuels by a process called Fischer-Tropsch synthesis.

"Over the last couple of years, our team has developed very high-performing catalysts for both the first and the second reactions," said Bo Zhang, a professor at Fudan University who contributed to the work. "But while the second catalyst works under neutral conditions, the first catalyst requires high pH levels in order to be most active."

New Discovery with Promising Results

The original use of two catalysts that required different conditions complicated the process and reduced the amount of energy that could be converted. The team has now developed a catalyst for the first reaction that works with a neutral pH and needs less electrical energy to power its reaction.

The team reports an overall power conversion efficiency of 64%, which exceeds earlier reported efficiencies by approximately 10%. The new catalyst is comprised of nickel, iron, cobalt and phosphorus, so it’s lower in cost and relatively safe. It can be made at room temperature, is relatively inexpensive, and has been shown to remain stable for at least 100 hours.

With this improved catalyst, the next step is to build their artificial photosynthesis system at pilot scale. Their goal is to capture CO₂ from flue gas (a natural gas-burning power plant, for example) and use the new catalytic system to efficiently convert it to liquid fuel.

“We have to determine the right operating conditions: flow rate, concentration of electrolyte, electrical potential,” said De Luna. “From this point on, it’s all engineering.”