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DGIST-led team improves efficiency of photocatalyst for conversion of atmospheric CO2 to hydrocarbon fuels

Researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST), with colleagues in Korea, Japan, and the US, have added copper and platinum nanoparticles to the surface of a blue titania photocatalyst, thereby significantly improving its ability to recycle atmospheric carbon dioxide into hydrocarbon fuels (methane and ethane).

The modified photocatalyst converted sunlight to fuel with a maximum efficiency of 3.3% over 30-minute periods.

Herein we report a photocatalyst, reduced blue-titania sensitized with bimetallic Cu–Pt nanoparticles that generates a substantial amount of both methane and ethane by CO2 photoreduction under artificial sunlight (AM1.5): over a 6 h period 3.0 mmol g−1 methane and 0.15 mmol g−1 ethane are obtained (on an area normalized basis 0.244 mol m−2 methane and 0.012 mol m−2 ethane), while no H2 nor CO is detected. This activity (6 h) translates into a sustained Joule (sunlight) to Joule (fuel) photoconversion efficiency of 1%, with an apparent quantum efficiency of φ = 86%. The time-dependent photoconversion efficiency over 0.5 h intervals yields a maximum value of 3.3% (φ = 92%).

—Sorcar et al.

This photoconversion efficiency is an important milestone, the researchers report in their study published in the journal 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 catalyze a chemical reaction. Scientists are investigating their use to trap carbon dioxide from the atmosphere as one of many means to alleviate global warming. Some photocatalysts are being tested for their ability to recycle carbon dioxide into hydrocarbon fuels such as methane, the main component found in natural gas.

Methane combustion releases less carbon dioxide into the atmosphere compared to other fossil fuels, making it an attractive alternative. But scientists have been finding it difficult to manufacture 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 property while platinum is very good at separating the much-needed charges generated by the blue titania from the sun’s energy.

The team developed a novel set-up to measure accurately 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 vapor moved through the chamber, passing over the catalyst. An analyzer measured the gaseous components coming out of the chamber as a result of the photocatalytic reaction.

203023_web

Fuel production efficiency of titanium dioxide photocatalyst with copper-platinum alloy co-catalyst (a) and a photo of photocatalyst observed by HRTEM (b). Credit ©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 commercialization.

—Prof. In

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.

Resources

  • Saurav Sorcar, Yunju Hwang, Jaewoong Lee, Hwapyong Kim, Keltin M. Grimes, Craig A. Grimes, Jin-Woo Jung, Chang-Hee Cho, Tetsuro Majima, Michael R. Hoffmannd and Su-Il In (2019) “CO2, water, and sunlight to hydrocarbon fuels: a sustained sunlight to fuel (Joule-to-Joule) photoconversion efficiency of 1%” Energy Environ. Sci. doi: 10.1039/C9EE00734B

Comments

Engineer-Poet

I'm sure that the people in the field know how to read between the lines here, but it would be nice to have an explanation of what happens to the oxygen in the feedstock for the enlightenment of non-specialists.

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