When researchers exposed a ‘spongy’ nickel organic crystalline structure to visible light, the material converts CO2 into carbon monoxide (CO) gas, which can then be turned into liquid fuels, solvents, and other products.
“We show a near 100% selectivity of CO production, with no detection of competing gas products like hydrogen or methane,” said Haimei Zheng, staff scientist in Berkeley Lab's Materials Sciences Division and co-corresponding author of the study. “That's a big deal. In carbon dioxide reduction, you want to come away with one product, not a mix of different things.”
The researchers developed an innovative laser chemical method of creating a metal-organic composite material. They dissolved nickel precursors in a solution of triethylene glycol and exposed the solution to an unfocused infrared laser, which set off a chain reaction in the solution as the metal absorbed the light. The resulting reaction formed metal-organic composites that were then separated from the solution.
"When we changed the wavelength of the laser, we would get different composites," said study co-lead author Kaiyang Niu, a materials scientist in Zheng's lab. "That's how we determined that the reactions were light-activated rather than heat-activated."
Scientists at NTU tested the new material in a gas chamber filled with carbon dioxide, measuring the reaction products using gas chromatography and mass spectrometry techniques at regular time intervals. They determined that in an hour at room temperature, 1g of the nickel-organic catalyst was able to produce 16,000 micromoles, or 400 milliliters, of carbon monoxide. Moreover, they determined that the catalyst had a promising level of stability that allowed it to be used for an extended time.
"The world right now is in need of innovative ways to create alternatives to fossil fuels, and to stem the levels of excessive CO2 in the atmosphere," said Zheng. "Converting CO2 to fuels using solar energy is a global research endeavour. The spongy nickel-organic photo-catalyst we demonstrated here is a critical step toward practical production of high-value multi-carbon fuels using solar energy."
