A pure water-fed membrane-electrode assembly system for the electrocatalytic reduction of carbon dioxide

Electrochemical reduction of carbon dioxide (CO)₂) into useful chemicals and raw materials, could help mitigate greenhouse gas emissions, allowing industries to reuse the released CO₂ in a beneficial way. Most of the strategies implemented so far to achieve this, however, have notable limitations, notably low stability over long periods.

Researchers from the Hong Kong Polytechnic University, the University of Oxford and the National Synchrotron Radiation Research Center recently introduced a new membrane-electrode assembly system that could facilitate stable electrocatalytic reduction of CO₂.

Notably, their proposed system, which was first presented in a paper published in Natural energyis powered by pure water (H₂O) and therefore does not rely on an alkaline electrolyte.

“Our modern society relies heavily on fossil fuels to power our economy, but the resulting CO₂ emissions pose a major threat to the climate,” Shu Ping Lau, co-author of the paper, told Tech Xplore. “We seek to harness and reintroduce massive amounts of CO₂ in the carbon cycle using electrocatalytic CO₂ reduction (ECO₂R) technology to combat this. However, previous research has shown that the stability of CEE₂The R system poses a major challenge, with current systems lasting less than 200 hours for ECO₂R-in ethylene (C₂H₄).”

In their recent work, Lau and co-workers attempted to overcome the limitations of existing systems for electrocatalytic CO.₂ reduction. Their goal is to create a new electrolysis architecture that suppresses carbonate formation during CEE.₂R and thus allows stable and prolonged operation.

“Our goal is to maintain an alkaline cathodic environment without involving alkaline metal cations, ultimately designing the APMA MEA (AEM+PEM membrane-electrode assembly) architecture with pure H.₂O as in anolyte,” Lau explained. “In our APMA MEA ECO₂R system, we created a path for CO₂ react with H₂O to produce C₂H₄ and O.H.^– at the cathode, while H₂O is oxidized to O₂ and H⁺ at the anode. The resulting OH^– and H⁺ then combine to form H₂O in the middle of the membranes.

The new system introduced by the researchers includes two distinct membranes (AEM and PEM), a cathode catalyst (Cu with stepped surface), an anodic catalyst (Pt/Ti) and pure water as anolyte. One of its most notable advantages is that it does not require any additional chemicals to initiate reactions and uses only pure H.₂O as electrolyte. This means it could easily be scaled up to an industrial level.

“Even more impressive, the APMA MEA architecture overcomes the thermodynamic limitation of CO₂ react with electrogenerated OH^– in carbonate, which prolongs the stability of the system,” said Lau. “With its durability and efficiency, our APMA MEA system has the potential to revolutionize CO₂ electrocatalysis technology and transform the modern fossil energy system.

During the first tests, the APMA MEA system introduced by this team of researchers obtained very promising results. Use only pure H₂O as an anolyte and in forward bias mode, it was found to effectively suppress carbonate formation during ECO₂R, extension, stability of CO₂ reduction in hydrocarbon C₂H₄ to reach an impressive 1,000 hours.

“Our breakthrough in creating a stable and sustainable ECO₂The R system is crucial to industrialize ECO₂R,” Lau said. “With the potential to move toward industrial-level tariffs, the APMA MEA system could pave the way for significant reductions in CO emissions₂ emissions on an industrial scale.

The promising methods and technologies introduced by Lau and his colleagues could soon be improved and evaluated, both in the laboratory and in the real industrial world. Ultimately, this could contribute to ongoing global efforts to reduce carbon emissions, by facilitating the electrocatalytic reduction of CO.₂.

“In our initial APMA MEA system, we encountered high operating voltage and low current density, which resulted in low yield of the desired product (C₂H₄) and low overall power efficiency,” Lau added. “Our next step is to focus on improving the current density and power efficiency of the APMA system while reducing the system overpotential.”

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