HYDROCARBONS BY ANY OTHER NAME...
New electrocatalyst converts CO2 into ethanol, acetone, and n-butanol with high efficiency
16 November 2021
The electrocatalytic conversion of CO2 using renewable energy could establish a climate-neutral, artificial carbon cycle. Excess energy produced by photovoltaics and wind energy could be stored through the electrocatalytic production of fuels from CO2. These could then be burned 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.
Now, researchers in China have developed a new electrocatalyst that yields ethanol, acetone, and n-butanol as major products with a total C2-4 faradaic efficiency of about 49 % at −0.8 V vs. reversible hydrogen electrode (RHE), which can be maintained for at least 3 months. A paper on the development is published in the journal Angewandte Chemie.
Credit: Angewandte Chemie
To make the electrocatalyst, the team from Foshan University (Foshan, Guangdong), the University of Science and Technology of China (Hefei, Anhui), and Xi’an Shiyou University (Xi’an, Shaanxi), led by Fei Hu, Tingting Kong, Jun Jiang, and Yujie Xiong, etched thin ribbons of a copper/titanium alloy with hydrofluoric acid to remove the titanium from the surface.
This results in the material a-CuTi@Cu, with a porous copper surface on an amorphous CuTi alloy. It has catalytically active copper centers with remarkably high activity, selectivity, and stability for the reduction of CO2 to C2+ products. 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.
Resources
Hu, F., Yang, L., Jiang, Y., Duan, C., Wang, X., Zeng, L., Lv, X., Duan, D., Liu, Q., Kong, T., Jiang, J., Long, R. and Xiong, Y. (2021), “Ultrastable Cu Catalyst for CO2 Electroreduction to Multicarbon Liquid Fuels by Tuning C–C Coupling with CuTi Subsurface.” Angew. Chem. Int. Ed.. https://doi.org/10.1002/anie.202110303
New technique to avoid CO2 in energy conversion processes with carbon-containing fuels
Nature knows several ways how to capture carbon dioxide (CO2). The most prominent one is photosynthesis, where sun light is used to fix CO2 into biomass. Nowadays, research groups around the world try hard to mimic this process and to realize artificial photosynthesis. The ultimate goal is to efficiently photo-transform CO2 into synthetic fuels. However, nature knows also other strategies for capturing carbon dioxide, such as dissolving CO2 as carbonate (CO32-) in the oceans. Shellfish then make use of the dissolved carbonate and build CaCO3-based solid structures for shelter, which finally end up safely in rocks around the globe.
Inspired by the way shellfishes capture carbon dioxide, LMU scientists at the Nano-Institute Munich developed the vision to transform a carbon-containing fuel into a carbon-free fuel without releasing CO2 but capture carbon as carbonate. They chose alkaline methanol and devised a light-triggered system, which efficiently produced hydrogen and carbonate in the form of tiny stones. They introduced a novel multi-layer device to make maximum use of the incident light and the catalysts. State-of-the-art activities in hydrogen evolution rates are obtained, even much higher than benchmark systems driven by heat. Dr. Yiou Wang, who performed most of the experimental work is a Fellow of the Alexander-von-Humboldt foundation working at the Chair for Photonics and Optoelectronics led by Prof. Jochen Feldmann. He remembers: "I had two moments of great excitement: First when I saw the hydrogen bubbles emerging on the catalyst and second when I noticed the carbonate crystals precipitating from the solution." Dr. Jacek Stolarczyk, an expert in artificial photosynthesis, adds: "Light is an excellent means of triggering energy conversion reactions, more convenient to use than heat and pressure."
A possible application is the in-situ production of required hydrogen from low-cost alcohols, which avoids the risks to store and transport hydrogen before use in fuel cells. Such a carbon-neutral and light-triggered process produces hydrogen safely and efficiently, which could enable scalable fabrication and hold promise for broad and practical applications. Prof. Jochen Feldmann states: "Avoiding CO2-emission by binding the carbon in carbonates might generally become an important concept when using carbon-containing fuels."Carbon capture process produces hydrogen and construction materials
More information: Yiou Wang et al, A Multi‐layer Device for Light‐triggered Hydrogen Production from Alkaline Methanol, Angewandte Chemie International Edition (2021). DOI: 10.1002/anie.202109979
Journal information: Angewandte Chemie International Edition
Provided by Ludwig Maximilian University of Munich
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