Cobalt copper tandem catalysts transform CO2 into renewable ethanol

Berlin, Germany (SPX) Nov 05, 2024
Researchers at Johannes Gutenberg University Mainz (JGU) have unveiled a pioneering approach to convert carbon dioxide (CO2) into ethanol, providing a sustainable alternative for chemical applications and energy storage. This technique, led by Professor Carsten Streb from JGU's Department of Chemistry, offers a pathway to repurpose CO2 emissions as part of a closed-loop carbon cycle, with the potential for wider use in industry. "We can remove the greenhouse gas CO2 from the environment and reintroduce it into a sustainable carbon cycle," said Streb.

His research focuses on transforming CO2 into ethanol through electrocatalysis. When combined with green energy sources, this process could reduce the reliance on food crops, such as corn, that are traditionally used to produce ethanol for fuel. Streb added that while the process currently operates on a laboratory scale, it holds promise for larger-scale applications. Findings from the study are now published in 'ACS Catalysis'.

Cobalt-Copper Catalysts Achieve High Selectivity in CO2 Conversion
The electrochemical transformation of CO2 to multicarbon compounds, such as ethanol, is an efficient way to capture CO2 and produce valuable materials for industrial use. However, success hinges on using catalysts that can achieve high selectivity, ensuring a high yield of ethanol. "To achieve this, we require suitable catalysts capable of this conversion with high selectivity so that we obtain a high yield of the desired product, which - in our case - is ethanol," explained Streb.

The research team engineered a specialized electrode, carefully coated with a black cobalt-copper powder in precise amounts and positioning. This tandem setup allows cobalt to initially break down the strong bonds within CO2, producing carbon monoxide. The copper component then catalyzes the conversion from carbon monoxide to ethanol, a process that only succeeds when both metals are correctly positioned on the electrode. "The initial challenge is to get carbon dioxide to react," said Streb. "The bonds between the atoms of the molecule are very strong, but cobalt can break them."

Boosting Efficiency for Broader Application
Currently, the method achieves 80 percent selectivity in converting CO2 to ethanol, the highest reported so far. Dr. Soressa Abera Chala, a lead author on the study, was instrumental in this optimization as a Humboldt Research Fellow at JGU. Co-authors Dr. Rongji Liu and Dr. Ekemena Oseghe also contributed to the research as Humboldt fellows. Efforts are underway to enhance this selectivity to between 90 and 95 percent, with the goal of eventually achieving 100 percent, where only ethanol is produced as the end product.

Collaborative Efforts Under CataLight
Collaboration with Ulm University as part of the Collaborative Research Center / Transregio "CataLight" (CRC/TRR 234) has been essential to this research. Through advanced electron microscopy, the team can observe individual atom placement on the catalyst, enabling them to refine the electrode's composition.

This focus on cobalt and copper stems from their abundance and affordability, which makes the process viable without costly precious metals like platinum. "We need to see the individual atoms, which is possible using a special kind of electron microscope," said Streb. This research aims to create a stable catalyst that maintains efficiency for extended periods.

A Sustainable Path to Ethanol Production
Producing ethanol from CO2 and green electricity presents an opportunity to alleviate the demand on food resources typically used for biofuel production. "By using globally available raw materials as catalysts, we are following an approach in current research to increasingly focus on non-precious metals," emphasized Streb.

This technology could supply sustainable ethanol, reducing reliance on agricultural crops like sugarcane and maize currently used in ethanol production, especially in regions such as Brazil. This development offers a scalable solution for producing ethanol that can be stored and used for power generation on demand.

SusInnoScience Research Context
Professor Streb, who joined JGU in 2022, is involved in several collaborative research projects on sustainable catalysis supported by German scientific and educational foundations. His work is part of JGU's Top Level Research Area SusInnoScience, which aims to promote sustainable chemical innovation for resource-efficient science.

+ Research group of Professor Carsten Streb at the JGU Department of Chemistry

+ JGU Top Level Research Area SusInnoScience - Sustainable chemistry as the key to innovation in resource-efficient science in the Anthropocene

+ CRC/Transregio 234: Light-Driven Molecular Catalysts in Hierarchically Structured Materials - Synthesis and Mechanistic Studies (CataLight), funded by the German Research Foundation (DFG)

Research Report:Selective Electroreduction of CO2 to Ethanol via Cobalt - Copper Tandem Catalysts