Novel Photocatalyst Speeds Conversion of Carbon Dioxide to Fuels

A titania photocatalyst has been developed that converts carbon dioxide (CO₂) into methane (CH₄ ) three times more efficiently than the existing photocatalyst. To achieve this result, the titania surface was manipulated.

Using a magnesiothermic reduction method, a research team from Daegu Gyeongbuk Institute of Science and Technology (DGIST) removed oxygen atoms from the surface of titanium dioxide (TiO₂), synthesizing an oxygen-deficient TiO₂.

A schematic diagram showing the mechanism of the conversion of carbon dioxide into methane using the reduced titanium dioxide developed by the team. Courtesy of DGIST.

The photocatalytic activity was investigated for CO₂/H₂O (gas) mixture conversion to methane. A platinum (Pt) co-catalyst was photodeposited and optimized for efficient charge separation.

According to the team, the newly developed photocatalyst illustrated controlled band gap by removing oxygen atoms on the surface of TiO₂ through the strong reduction of magnesium and hydrogen. This band gap control improved the light absorption and optimized the efficient charge separation. As a result, the photocatalyst was found to increase the conversion rate of carbon dioxide into methane up to threefold compared to the existing photocatalyst.

A graph comparing methane production efficiencies between the existing photocatalyst and new photocatalyst developed by the team. Courtesy of DGIST.

The researchers attribute the improved photocatalytic performance to enhanced light absorption, efficient separation of photogenerated charges, and suitable band edge alignment with respect to the carbon dioxide/methane reduction (redox) potential.

Results suggest that the Pt-sensitized reduced TiO₂ could serve as an efficient photocatalyst for solar light CO₂ photoreduction.

The study also shows the usefulness of the current magnesiothermic reduction method, which was applied for the preparation of the reduced titanium dioxide photocatalyst through a relatively simple thermoreduction method with magnesium metal and hydrogen gas.

Professor Su-Il In said, “The key of this study is that we have improved the efficiency of the existing titanium dioxide photocatalyst by using a relatively simple magnesiothermic reduction method. By understanding the conversion mechanism of carbon dioxide into hydrocarbon, we expect to apply it to use carbon dioxide as resource in abatement technologies.”

DGIST's joint research team. From left are professor Su Il-in and professor Jong-Sung Yu. Courtesy of DGIST.

In order to control atmospheric CO₂ concentration, many countries are actively investigating ways to transform carbon dioxide into chemical fuels such as methane, ethane and methanol. A high-efficiency photocatalyst could help prevent the generation of secondary harmful substances when carbon dioxide is being converted into chemical fuels.

The research was published in Applied Catalysis B: Environmental (doi: 10.1016/j.apcatb.2017.05.028).