Titania photocatalyst recycles CO2 into hydrocarbons

A titania photocatalyst could recycle more atmospheric carbon dioxide into hydrocarbon fuels with copper and platinum nanoparticles added to its surface.

Titania photocatalyst
CO2 could be converted into methane

This is the claim of researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST), who developed and tested the modified photocatalyst with colleagues in Korea, Japan, and the US.

It is said to have converted sunlight to fuel with an efficiency of 3.3 per cent over 30-minute periods. This ‘photoconversion efficiency’ is an important milestone, the researchers report in their study published in Energy and Environmental Science, as it means that large-scale use of this technology is becoming a more realistic prospect.

Photocatalysts are semiconducting materials that can use the energy from sunlight to catalyse a chemical reaction. Scientists are investigating their use to trap carbon dioxide from the atmosphere as a way of alleviating global warming.

According to DGIST, some photocatalysts are being tested for their ability to recycle carbon dioxide into hydrocarbon fuels like methane, the main component found in natural gas. They say that methane combustion releases less carbon dioxide into the atmosphere compared to other fossil fuels, making it an attractive alternative. Scientists have, however, had difficulties manufacturing photocatalysts that produce a large enough yield of hydrocarbon products for their use to be practical.

Professor Su-Il In of DGIST’s Department of Energy Science and Engineering and his colleagues modified a blue titania photocatalyst by adding copper and platinum nanoparticles to its surface.

Copper has good carbon dioxide adsorption properties while platinum is very good at separating the charges generated by the blue titania from the sun’s energy.

To accurately measure the catalyst’s photoconversion efficiency the catalyst was placed in a chamber that received a quantifiable amount of artificial sunlight. Carbon dioxide gas and water vapour moved through the chamber, passing over the catalyst. An analyser measured the gaseous components coming out of the chamber as a result of the photocatalytic reaction.

According to DGIST, the blue titania catalyst converts the energy in sunlight into charges that are transferred to the carbon and hydrogen molecules in carbon dioxide and water to convert them into methane and ethane gases. The addition of copper and platinum nanoparticles on the catalyst’s surface was found to significantly improve the efficiency of this process.

“The photocatalyst has a very high conversion efficiency and is relatively easy to manufacture, making it advantageous for commercialisation,” Prof In said in a statement.

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