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A research team led by Professor Ying WANG, Assistant Professor from the Department of Chemistry at The Chinese University of Hong Kong (CUHK), has developed an electrochemical system, acidic CO₂ electrolyser, to convert carbon dioxide (CO₂) and water (H₂O) with renewable electricity into valuable chemical raw materials, providing a promising low-carbon alternative for fossil fuel-based materials in chemical industries. The work has achieved a CO₂ utilisation efficiency as high as 60% in the conversion process. The result has been recently published in Nature Catalysis, one of the world’s leading scientific journals.

Low carbon utilisation is the biggest limitation of current CO₂ electrolyser technology

Mitigating emissions of greenhouse gases is an important way to combat global warming, but cutting the concentration of atmospheric carbon dioxide is of equal importance. Close to 80% of overall CO₂ emissions on Earth come from the combustion of fossil fuels for chemosynthesised raw materials valuable to compositing cosmetics, detergents, plastics and more. Carbon capture and conversion technology like CO₂ reduction reaction (CO₂RR) is therefore among the most promising means to reduce reliance on fossil fuels, capturing CO₂ emissions from industrial processes and converting the CO₂ into raw materials for the production of these chemical products.

At present, electrochemical CO₂RR usually operates in alkaline reactors or electrolytes, during which more than 85% of CO₂ is consumed by the electrolyte, leading to the formation of carbonate, requiring extensive energy and cost to further capture and convert CO₂, and resulting in a low carbon utilisation rate of 25% and poor cost effectiveness.

Novel acidic CO₂ electrolyser with palladium-copper catalyst boosts carbon utilisation efficiency

To overcome the low carbon utilisation rate and the loss of CO₂ during conversion, Professor Wang worked with a research team from the Department of Electrical and Computer Engineering, University of Toronto to develop a novel acidic CO₂ electrolyser that effectively suppresses carbonate formation. The team synthesised palladium-copper (Pd-Cu) catalyst to further suppress the issue of hydrogen evolution reaction (HER) brought by an acidic condition, and successfully raised the carbon utilisation rate to 60%, under the industrial condition of current density at 500 mA/cm². This allows more captured CO₂ to be converted to valuable raw materials needed for synthesised chemicals, such as ethylene.

Professor Wang said, “The rational design of catalyst and reactor in this work breaks the theoretical limit of carbon utilisation efficiency in current alkaline CO₂RR electrolysers, and contributes to the development of environmental technology. The leap in the conversion rate of CO₂ in acidic electrolysers advances this green technology towards an economically viable future. Now we are working on scaling up the technology to commercialise it.”

The full research paper can be found at: https://www.nature.com/articles/s41929-022-00788-1

About Professor Ying WANG

Professor Wang joined CUHK in 2019. Her research group focuses on understanding and device engineering for electrocatalysis. This project was funded by the Early Career Scheme under the Research Grant Council.