Scientists have created a copper catalyst that effectively converts carbon dioxide into acetaldehyde, which is an important chemical in manufacturing. This development presents an eco-friendly alternative to processes that depend on fossil fuels.
Acetaldehyde is essential for producing a variety of products, including perfumes and plastics. Currently, its creation predominantly relies on ethylene, a chemical derived from fossil fuels. However, rising environmental concerns are urging the chemical sector to diminish its dependence on these fuels; thus, researchers are exploring more sustainable methods for producing acetaldehyde.
Currently, acetaldehyde is generated via the “Wacker process,” which involves a chemical synthesis that combines ethylene obtained from oil and natural gas with strong acids like hydrochloric acid. This process has a significant carbon footprint, consumes a lot of resources, and is not sustainable in the long run.
A promising alternative is the electrochemical reduction of carbon dioxide (CO2) into valuable products. Since CO2 is a waste product contributing to global warming, this method addresses two environmental issues simultaneously: it lessens CO2 emissions and generates useful chemicals.
An innovative catalyst for better performance
Copper-based catalysts have shown promise for this transformation, but up until now, they have been limited by low selectivity, meaning they produce a mix of products rather than solely acetaldehyde.
Recently, scientists from a public-private collaboration, led by Cedric David Koolen of EPFL and including Jack K. Pedersen from the University of Copenhagen and Wen Luo from Shanghai University, have developed a new copper catalyst that selectively converts CO2 into acetaldehyde with a remarkable efficiency of 92%.
This advancement, published in Nature Synthesis, offers a greener and more sustainable method to produce acetaldehyde, potentially replacing the Wacker process. Additionally, the catalyst is economically viable and can be scaled up for industrial use.
“The Wacker process has essentially remained unchanged for the last 60 years and is still based on the same fundamental chemistry. It was time for a green innovation,” states Koolen.
“Intriguing chemistry”
The researchers began their work by creating tiny clusters of copper particles, each about 1.6 nanometers wide, using a technique known as spark ablation. This method vaporizes copper electrodes in an inert gas environment, allowing precise control over particle sizes. The copper clusters were then immobilized on carbon supports to create a stable catalyst that can be reused.
In the laboratory, the team evaluated the catalyst’s performance by conducting a series of electrochemical reactions with CO2 in a controlled setting. Using a synchrotron—a large facility that produces a bright light source—the researchers verified that the copper clusters were actively transforming CO2 into acetaldehyde using X-ray absorption spectroscopy.
The outcomes were remarkable. The copper clusters achieved a 92% selectivity for acetaldehyde at relatively low voltages, which is crucial for energy effectiveness. In a 30-hour stress test, the catalyst exhibited high stability, maintaining its performance over several cycles. The researchers also observed that the copper particles retained their metallic state throughout the reactions, contributing to the catalyst’s durability.
“What surprised us was that the copper stayed metallic, even after being exposed to air and removing the voltage,” explained co-lead author Wen Luo. “Copper typically oxidizes rapidly, especially at such small sizes. However, in our case, an oxide shell formed around the cluster, shielding the core from further oxidation. This explains the material’s recyclability—it’s fascinating chemistry.”
The keys to success
What made the new catalyst function so efficiently? Computational simulations indicated that the configuration of atoms in the copper clusters encourages CO2 molecules to connect and transform in a way that favors acetaldehyde production over other possible outcomes, such as ethanol or methane.
“The great advantage of our method is that it can be adapted to any other catalyst system,” remarked co-lead author Jack K. Pedersen. “With our computational approach, we can swiftly screen clusters for advantageous traits. Whether for CO2 reduction or water electrolysis, we can easily produce the new material with spark ablation and test it in the lab directly, significantly speeding up the testing process compared to traditional cycles.”
The new copper catalyst marks an important advancement towards greener industrial chemistry. If implemented on a larger scale, it could replace the Wacker process, decreasing the dependency on petrochemicals and lowering CO2 emissions. Given that acetaldehyde serves as a foundational building block for numerous other chemicals, this research has the potential to impact various sectors, including pharmaceuticals and agriculture.
