Ionic liquid catalyst could help turn emissions into fuel

The catalyst is claimed to overcome a major obstacle to producing technology that simultaneously reduces atmospheric carbon dioxide and produces fuel.

Paul Kenis, professor of chemical and biological engineering at the University of Illinois, and his research group joined forces with researchers at Dioxide Materials to produce the catalyst, which is described in a paper published in the journal Science.

Artificial photosynthesis is the process of converting carbon-dioxide (CO₂) gas into useful carbon-based chemicals, most notably fuel or other compounds usually derived from petroleum, as an alternative to extracting them from biomass.

However, artificial photosynthesis has been kept from the mainstream because the process is too energy intensive.

The first step to making fuel requires turning CO₂ into carbon monoxide. This process requires so much electricity to drive, more energy is used to produce the fuel than it can store.

The Illinois group claims to have overcome this major hurdle by introducing an ionic liquid to catalyse the reaction, greatly reducing the energy required to drive the process.

The ionic liquids stabilise 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, which uses energy from a solar collector or a wind turbine, to separate gaseous CO₂ and oxygen output from the liquid electrolyte catalyst with gas-diffusion electrodes.

The CO₂ is then converted into simple carbon fuels such as formic acid or methanol, which are further refined to make ethanol and other fuels.

‘It lowers the overpotential for CO₂ reduction tremendously,’ said Kenis, who is also a professor of mechanical science and engineering and affiliated with the Beckman Institute for Advanced Science and Technology. ‘Therefore, a much lower potential has to be applied. Applying a much lower potential corresponds to consuming less energy to drive the process.’

In plants, photosynthesis uses solar energy to convert CO₂ and water to sugars and other hydrocarbons. Biofuels are refined from sugars extracted from crops such as corn, but this isn’t necessary with artificial photosynthesis.

‘The key advantage is that there is no competition with the food supply,’ said Richard Masel, a co-principal investigator of the paper and chief executive officer of Dioxide Materials, ‘and it is a lot cheaper to transmit electricity than it is to ship biomass to a refinery.’

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 maximise conversion.

‘More work is needed, but this research brings us a significant step closer to reducing our dependence on fossil fuels while simultaneously reducing CO₂ emissions that are linked to unwanted climate change,’ Kenis said.