Expanding Catalyst Family for Electrocatalytic Reduction of CO2

By Shaheer RehanReviewed by Megan Craig, M.Sc.Jul 21 2022

For electrolytic reduction of carbon dioxide (CO₂), copper (Cu) distributed on 2D materials demonstrates outstanding catalytic activity. In a paper published in The Journal of Physical Chemistry C, a new kind of 2D nanoscale catalyst was developed by mounting clusters of copper on defective diamond graphene.

Study: Anchoring Cu Clusters over Defective Graphene for Electrocatalytic Reduction of CO2. Image Credit: Victor Josan/Shutterstock.com

Addressing the Ever-Increasing CO₂ Content in the Atmosphere

Carbon dioxide (CO₂) is the most well-known greenhouse gas and a principal contributor to the drastic climate change which has taken the world by storm. Therefore, collecting and recycling CO₂ into value-added goods and fuels is critical.

CO₂ is primarily produced by the burning of fossil fuels and petrochemical refineries, as well as the cement, iron, and steel production industries. Without a doubt, the contribution of CO₂ toward the greenhouse effect and global warming is unmatched.

One possible approach to establishing a balanced carbon cycle is to utilize CO₂ as a carbon-containing resource for manufacturing valuable organic substances such as methanol and methane. CO₂ may be transformed into a number of carbon-based materials using processes like electrochemical, photochemical, and biological reduction.

CO₂ Reduction Reaction Needs a Catalyst

The electrochemical reduction process of CO₂ shows good reaction speeds and CO₂ transformation rates. Nonetheless, CO₂ molecules have a non-polar linear makeup and are chemically inert and thermodynamically stable. This high stability necessitates extreme temperature and pressure settings for its electrochemical reduction procedure.

CO₂ may be activated by using appropriate catalysts. So, developing an effective CO₂ reduction reaction catalyst with excellent product specificity and minimal overpotential is urgently needed.

Benefits of Using Copper Catalysts

Different materials, including transition metals, precious metals, and metallic oxides, have been explored for the catalysis of CO₂ reduction reactions. Copper (Cu) is a nontoxic transition metal, abundantly available, highly selective and an effective catalyst.

Various kinds of copper materials can be used to generate oxygenates and hydrocarbons, applying different potentials. The electrochemical reduction reaction of CO₂ using raw Cu requires a significant overpotential, making the process highly energy intensive.

The set of proton-coupled electron-transference steps may be successfully enhanced by modifying the copper-based nanoarchitecture, considerably increasing catalytic performance.

Copper catalysts generate a broader spectrum of products than other metal-based catalysts because of how electrocatalytic performance is affected by the magnitude of clusters and exposure to air.

For optimizing the structure of the electrocatalyst and adjusting exposure to air, surface nanostructuring and regulated electrophoretic deposition are known to be effective techniques. Such catalysts could well prove to be suitable for industrial manufacturing.

Graphene Platforms can Enhance Copper's Catalytic Effects

Ever since graphene was discovered, this sophisticated 2D material has been the focus of research in catalyzed conversion and energy storage. The controlled transformation of ethyne to ethene may be achieved by depositing copper atoms onto faulty diamond graphene.

The exposed fraction of the Cu clusters and the hardness of the composite depend on the copper-carbon bond's distinctive structure. Efficient electron transfer may enhance the catalytic performance of the unsaturated coordination spots.

What Did the Researchers Do?

In this study, the team developed copper clusters that could be firmly attached to defective nanodiamond graphene. The copper atoms were distributed on 2D materials and could be employed as a unique CO₂ reduction reaction catalyst.

The team believed that testing procedures would allow control of the aggregating mechanism and quantity of the attached copper clusters on the graphene platform to satisfy the demands of practical manufacturing.

Important Findings

Copper clusters with varied atomic numbers and interaction mechanisms will yield diverse catalyzed products. Inverted triangle Cu₃/ND@G and triangular Cu₄/ND@GR accelerated the CO₂ reduction reaction with analogous active sites and almost identical intermediates and path trends.

The adsorption capability of CO* intermediates is critical in the generation of various CO₂ reduction reaction products. CO* has a poor capacity to attach to the catalytic material on Cu₂/ND@G, and the CO* species break down into hazardous carbon monoxide gas. In comparison, CO* has a great binding capacity to the catalytic material in Cu₃/ND@G and will not detach, which leads to its thorough reduction into organic molecules.

The capability of the oxygen atoms to link with the catalytic material is critical for the formation of methanol or methane. Methanol will form if the carbon-oxygen linkage in the intermediate has significant binding potential. By modifying the stepped voltage amount, byproduct formation may be decreased.

The researchers predicted that this work could add to the existing group of CO₂ catalysts, expand the applications of graphene-supported transition metals, and offer a variety of concepts for developing novel CO₂ reduction reaction catalysts.

Reference

Du, D., Zhu, H. et al. (2022). Anchoring Cu Clusters over Defective Graphene for Electrocatalytic Reduction of CO₂. The Journal of Physical Chemistry C. Available at: https://pubs.acs.org/doi/10.1021/acs.jpcc.2c03551

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