CONVERTING CO2 INTO SUSTAINABLE FUELS

Did you know? While methane is a gas also known to contribute to climate change, methane combustion actually releases less carbon dioxide into the atmosphere than other fossil fuels, making it an attractive alternative. Methane is also being considered as an alternative to toxic and cancer-causing hydrazine-based fuels for propelling rocket engines.

Credit: DGIST Credit: DGIST

A blue titania photocatalyst (blue) modified with copper and platinum nanoparticles (brown and silver) improves the conversion of carbon dioxide (black/red) and water vapour (red/white) into methane and ethane (black/white) that can be used as fuel. Oxygen is released as a byproduct (red).

A material aims to deliver a one-two punch: recycling atmospheric carbon dioxide for the production of more sustainable hydrocarbon fuels.

A blue titania photocatalyst becomes much better at recycling atmospheric carbon dioxide into hydrocarbon fuels when copper and platinum nanoparticles are added to its surface.

Photocatalysts are semiconducting materials that use energy from sunlight to catalyse a chemical reaction. Researchers are investigating their use to trap harmful carbon dioxide from the atmosphere to help alleviate global warming. Some also want to take the process a step further: recycling the trapped carbon dioxide into hydrocarbon fuels like methane, the main component found in natural gas. However, it has been difficult to manufacture photocatalysts that yield large enough fuel volumes for their use to be practical.

Researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST), with colleagues in Korea, Japan, and the US, modified a blue titania photocatalyst by adding copper and platinum nanoparticles to its surface. Copper adsorbs carbon dioxide well, while platinum separates the charges generated by the blue titania from the sun’s energy to catalyse the conversion of carbon dioxide into fuel.

They found the modified photocatalyst was 3.3% efficient at using sunlight to convert carbon dioxide into fuel when calculated over separate 30-minute periods. This is ten times better than previous versions. The researchers note this is an important milestone, but that it will take time to make the technology commercially viable.

“The current work can serve as a launch pad for developing high performance photocatalysts,” says DGIST engineer Su-Il In.

The team developed a unique set up to accurately measure the catalyst’s photoconversion efficiency. They placed the catalyst in a chamber that received a quantifiable amount of artificial sunlight. Carbon dioxide gas and water vapour moved through the chamber over the catalyst. An analyser measured the gaseous components coming out of the chamber as a result of the photocatalytic reaction.

The team plans to continue its efforts to further improve the catalyst’s photoconversion efficiency, to make it thick enough to absorb all incident light, and to improve its mechanical integrity to enable easier handling.

“Photovoltaics were initially considered a tough dream to realise, but now have become one of the key solutions to fossil fuels,” In says. “Similarly, we believe artificial photosynthesis will one day become a widespread technology for recycling carbon dioxide into more sustainable fuels.”