Novel Catalyst Helps Turn Carbon Dioxide Into Fuel
- Friday, 07 October 2011
Artificial photosynthesis is the process of converting carbon dioxide gas into useful carbon-based chemicals - most notably fuel or other compounds usually derived from petroleum - as an alternative to extracting them from biomass. An Illinois research team has produced a catalyst that improves the process.
University of Illinois chemical and biological engineering professor Paul Kenis and his research group joined forces with researchers at Dioxide Materials, a startup company, to produce the catalyst. The company was founded by retired chemical engineering professor Richard Masel.
In plants, photosynthesis uses solar energy to convert carbon dioxide (CO2) and water to sugars and other hydrocarbons. Biofuels are refined from sugars extracted from crops such as corn. However, in artificial photosynthesis, an electrochemical cell uses energy from a solar collector or a wind turbine to convert CO2 to simple carbon fuels such as formic acid or methanol, which are further refined to make ethanol and other fuels.
“The key advantage is that there is no competition with the food supply, and it is a lot cheaper to transmit electricity than it is to ship biomass to a refinery,” said Masel
However, one hurdle has kept artificial photosynthesis from becoming mainstream: The first step to making fuel, turning carbon dioxide into carbon monoxide, is too energy intensive. It requires so much electricity to drive this first reaction that more energy is used to produce the fuel than can be stored in the fuel.
The Illinois group used a novel approach involving an ionic liquid to catalyze the reaction, greatly reducing the energy required to drive the process. The ionic liquids stabilize the intermediates in the reaction so that less electricity is needed to complete the conversion.
The researchers used an electrochemical cell as a flow reactor, separating the gaseous CO2 input and oxygen output from the liquid electrolyte catalyst with gas-diffusion electrodes. The cell design allowed the researchers to fine-tune the composition of the electrolyte stream to improve reaction kinetics, including adding ionic liquids as a co-catalyst.
“It lowers the overpotential for CO2 reduction tremendously,” said Kenis. “Therefore, a much lower potential has to be applied. Applying a much lower potential corresponds to consuming less energy to drive the process.”
Next, the researchers hope to tackle the problem of throughput. To make their technology useful for commercial applications, they need to speed up the reaction and maximize conversion.