CHICAGO—Forget photovoltaics and electricity—a team of researchers at the University of Illinois at Chicago (UIC) is looking to kick fossil fuels and power the world economy with photosynthetics.
Publishing their findings late last week in the academic journal Science, the team has developed a cheap and efficient solar cell that converts atmospheric carbon dioxide into synthetic hydrocarbon fuel using only sunlight.
“The new solar cell is not photovoltaic—it’s photosynthetic,” Amin Salehi-Khojin, the study’s senior author and assistant professor of mechanical and industrial engineering at UIC, said in a statement.
“Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight,” he added.
Unlike traditional solar cells, which convert the sun’s energy into electricity, the lab-scale device converts CO2 from the air into a mixture of hydrogen gas and carbon monoxide. The synthetic gas can then be burned directly or converted into hydrocarbon fuels. The researchers compared the photosynthetic process to how plants use photosynthesis to generate sugars—only instead of sugars, the new solar cell creates an energy-dense fuel.
A longtime goal of researchers around the world, reversing chemical combustion reactions and producing man-made fuels could make fossil fuels obsolete and greatly reduce the global greenhouse gas emissions they generate. According to Salehi-Khojin though, most other attempts at reversing the combustion process have been either inefficient, or reliant on expensive precious metals, so far.
“What we needed was a new family of chemicals with extraordinary properties,” he said.
To achieve the reaction more efficiently, the UIC team turned to a family of nano-structured compounds known as transition metal dichalcogenides. The researchers combined a range of TMDCs—which serve as catalysts—with an unconventional ionic liquid electrolyte in a three-electrode electrochemical cell to determine which compound would perform the function best. Eventually settling on nanoflake tungsten diselenide, the study’s lead author and UIC postdoctoral student, Mohammad Asadi, said the new catalyst is 1,000-times faster than noble-metal catalysts and about 20-times cheaper.
“The new catalyst is more active; more able to break carbon dioxide’s chemical bonds,” Asadi said.
Essentially an 18-square-centimetre artificial leaf, the solar cell prototype generates hydrogen and carbon monoxide gas at its cathode, and free oxygen and hydrogen ions at its anode, when it is energized by the sun.
“The hydrogen ions diffuse through a membrane to the cathode side, to participate in the carbon dioxide reduction reaction,” Asadi said.
The team has filed a provisional patent for the technology, and said it should be adaptable to both large- and small-scale applications. Further research will determine whether or not technology will become economically viable.
The UIC researchers are not the only team working to synthesize fossil fuels from atmospheric CO2, however. Among other projects worldwide, Carbon Engineering, a cleantech company based in Squamish, B.C., is currently piloting its carbon-scrubbing technology that draws in CO2 from the air, isolating it for synthesis or sequester.