IU team creates efficient nanographene-Re electro- and photo-catalyst for efficient reduction of CO2 to CO
Researchers at Indiana University Bloomington have a nanographene–Re (Rhenium) complex that functions as an efficient electrocatalyst and photocatalyst for the selective reduction of CO2 to CO for subsequent conversion to fuels.
The complex can selectively electrocatalyze CO2 reduction to CO in tetrahydrofuran at −0.48 V vs NHE—the least negative potential reported for a molecular catalyst. In addition, the complex can absorb a significant spectrum of visible light to photo-catalyze the chemical transformation without the need for a photo-sensitizer. A report on their work is published in the Journal of the American Chemical Society.
If you can create an efficient enough molecule for this reaction, it will produce energy that is free and storable in the form of fuels. This study is a major leap in that direction.— Liang-shi Li, corresponding author
A major goal among scientists has been decreasing the excess energy needed to convert captured carbon dioxide back into fuel. The new molecule requires the least amount of energy reported thus far to drive the formation of carbon monoxide. The molecule—a nanographene-rhenium complex connected via an organic compound known as bipyridine—triggers a highly efficient reaction that converts carbon dioxide to carbon monoxide.
The ability to create carbon monoxide efficiently and exclusively is significant due to the molecule’s versatility.
The secret to the molecule’s efficiency is nanographene—a nanometer-scale piece of graphite—because the material’s dark color absorbs a large amount of sunlight.
Li said that bipyridine-metal complexes have long been studied to reduce carbon dioxide to carbon monoxide with sunlight. But these molecules can use only a tiny sliver of the light in sunlight, primarily in the ultraviolet range, which is invisible to the naked eye. In contrast, the molecule developed at IU takes advantage of the light-absorbing power of nanographene to create a reaction that uses sunlight in the wavelength up to 600 nanometers—a large portion of the visible light spectrum.
Essentially, the molecule acts as a two-part system: a nanographene “energy collector” that absorbs energy from sunlight and an atomic rhenium “engine” that produces carbon monoxide. The energy collector drives a flow of electrons to the rhenium atom, which repeatedly binds and converts the normally stable carbon dioxide to carbon monoxide.
|The new molecule employs a nanographene complex (on left) to absorb light and drive the conversion of carbon dioxide (upper center) to carbon monoxide (on right). Photo by Ben Noffke and Richard Schaugaard. Click to enlarge.|
The idea to link nanographene to the metal arose from Li’s earlier efforts to create a more efficient solar cell with the carbon-based material.
Next, Li plans to make the molecule more powerful, including making it last longer and survive in a non-liquid form, since solid catalysts are easier to use in the real world. He is also working to replace the rhenium atom in the molecule—a rare element—with manganese, a more common and less expensive metal.
This study was supported by IU Office of the Vice Provost for Research and the National Science Foundation.
Xiaoxiao Qiao, Qiqi Li, Richard N. Schaugaard, Benjamin W. Noffke, Yijun Liu, Dongping Li, Lu Liu, Krishnan Raghavachari, and Liang-shi Li (2017) “Well-Defined Nanographene–Rhenium Complex as an Efficient Electrocatalyst and Photocatalyst for Selective CO2 Reduction” Journal of the American Chemical Society doi: