A New Electrocatalyst Converts CO2 Into Liquid Fuels

A new electrocatalyst called a-CuTi@Cu converts carbon dioxide (CO₂ ) into liquid fuels. An active copper centered on an amorphous copper/titanium alloy produces ethanol, acetone, and n-butanol with high efficiency.

The research has been reported by a team of Chinese researchers in the journal Angewandte Chemie. The team includes members from from Foshan University (Foshan, Guangdong), the University of Science and Technology of China (Hefei, Anhui), and Xi’an Shiyou University (Xi’an, Shaanxi), and are led by Fei Hu, Tingting Kong, Jun Jiang, and Yujie Xiong.

Most of our global energy demands are still being met by burning fossil fuels, which contributes to the release of CO₂. To reduce CO₂ releases, we must look for opportunities to use and recycle CO₂ as a raw material for basic chemicals.

Through electrocatalytic conversion of CO₂ using renewable energy, a climate-neutral, artificial carbon cycle could be established. Excess energy produced by photovoltaics and wind energy could be stored through the electrocatalytic production of fuels from CO₂. These could then be combusted as needed.

Conversion into liquid fuels would be advantageous because they have high energy density and are safe to store and transport. However, the electrocatalytic formation of products with two or more carbon atoms (C₂₊) is very challenging.

The team has developed a novel electrocatalyst that efficiently converts CO₂ to liquid fuels with multiple carbon atoms (C_2-4). The primary products are ethanol, acetone, and n-butanol.

To make the electrocatalyst, thin ribbons of a copper/titanium alloy are etched with hydrofluoric acid to remove the titanium from the surface. This results in a material named a-CuTi@Cu, with a porous copper surface on an amorphous CuTi alloy.

The alloy has catalytically active copper centers with remarkably high activity, selectivity, and stability for the reduction of CO₂ to C₂₊ products (total faradaic efficiency of about 49% at 0.8 V vs. reversible hydrogen electrode for C_2-4 (the number of carbon atoms in the respective molecule) and it is stable for at least three months). In contrast, pure copper foil produces C₁ products but hardly any C₂₊ products.

The reaction involves a multistep electron-transfer process via various intermediates. In the new electrocatalyst, the inactive titanium atoms below the surface actually play an important role; they increase the electron density of the Cu atoms on the surface. This stabilizes the adsorption of *CO, the key intermediate in the formation of multicarbon products, allows for high coverage of the surface with *CO, and lowers the energy barrier for di- and trimerization of the *CO as new carbon-carbon bonds are formed.

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This report follows the one last week that offered a natural gas product (a C₁ product) from CO₂. But this time the results are in the C_2-4 range – that offers more variety. This technology has just popped from an idea into reality and looks to be taking off fast. How far and fast it can get is anyone’s guess for now. A rooftop fuel making device may have a lot more consumer appeal than a solar panel array. We’re going to be watching this technology.

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