Copper Nanoclusters Could Be New Catalyst for Converting CO2 Into Methane, Show Potential in Reducing Effects of Climate Change

A new study suggests that using copper to turn carbon dioxide into methane may prove to be a game changer in mitigating climate change.

Conversion of CO2 to Methane

Carbon dioxide from human-generated activities is the biggest source of global warming. By 2020, atmospheric carbon dioxide concentration had increased by 48% from the level before pre-industrialization, which was before 1750.

One of the climate change mitigation measures is carbon capture, a technique where CO2 is captured from burning fossil fuels before being released into the atmosphere. The process seems to be quite expensive since the cost of carbon capture and storage (CSS) is estimated between $15- $130 per metric ton of carbon dioxide.

To make carbon capture more economical, researchers are trying to convert captured carbon dioxide into methane, the main constituent of natural gas. However, the traditional method of producing methane from fossil fuels introduces more carbon dioxide into the atmosphere.

Electrocatalysis for CO2-Methane Conversion

At the University of Saskatchewan, a group of researchers looked to contribute towards some of the current shortcomings in methane production and progress in sustainable utilization of CO2 in energy systems. In the paper "Copper nanoclusters: Selective CO2 to methane conversion beyond 1 A/cm²," scientists described electrocatalysis as a new process for creating methane.

Led by Mahdi Salehi, the research team used copper nanoclusters to transform atmospheric carbon dioxide into methane. Once the methane is used, any carbon dioxide released can be captured and recycled back into methane.

The process thus can constitute a closed cycle of carbon, without emitting any new carbon dioxide into the atmosphere.

In their simulations, the team used copper catalysts of various sizes, from small ones with only 19 atoms to larger ones with 1000 atoms. Then, these were tested in the laboratory, focusing on how the sizes of the clusters affected the reaction mechanism.

Salehi and colleagues discovered that extremely small copper nanoclusters are very effective at producing methane. They observed a clear shift in selectivity from ethylene to methane as particle size decreased.

These extremely small-sized particles show maximum stability since they assume a pyramid structure.

In particular, researchers obtained high-alkaline electrolytes with an exceptional Faradaic efficiency (FE) of 85% and a maximum partial current density of 1.2 A/cm2. Such a result is very important, as it proves that the size and structure of copper nanoclusters turned out to be very vital for the reaction outcome.

It has also been observed that smaller particles with copper as the dominating facet not only improve the methane pathway but also strongly adsorb any ethylene produced onto the nanocluster, which further gets converted into methane. The observation also suggests that multi-carbon product formation can ideally take place with even the aid of alkaline electrolytes, which most likely will end up in the formation of methane.

Understanding the relationship between particle size, crystallinity, and the novel reaction mechanism on nanoclusters provides new avenues for designing a superior form of catalyst that allows the production of previously unattainable products.

In the future, the research team plans to continue refining their catalyst to make it more efficient with large-scale industrial applications. They are optimistic that their findings will open new opportunities for producing clean, sustainable energy.

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